Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.91	6.713%	$127.9596	$127.96	$127.95	$128.00
Purchase #2	$230.78	8.864%	$251.2363	$251.24	$251.25	$251.20
Purchase #3	$250.31	5.607%	$264.3449	$264.34	$264.35	$264.30
Purchase #4	$159.38	12.346%	$179.0571	$179.06	$179.05	$179.10
Purchase #5	$189.28	12.403%	$212.7564	$212.76	$212.75	$212.80
Purchase #6	$133.92	5.580%	$141.3927	$141.39	$141.40	$141.40
Purchase #7	$216.44	11.280%	$240.8544	$240.85	$240.85	$240.90
7 purchase totals =	$1,300.02		$1,417.6014	$1,417.60	$1,417.60	$1,417.70