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	$147.77	11.261%	$164.4104	$164.41	$164.40	$164.40
Purchase #2	$149.69	6.408%	$159.2821	$159.28	$159.30	$159.30
Purchase #3	$243.36	8.693%	$264.5153	$264.52	$264.50	$264.50
Purchase #4	$66.50	10.684%	$73.6049	$73.60	$73.60	$73.60
Purchase #5	$124.29	10.330%	$137.1292	$137.13	$137.15	$137.10
Purchase #6	$122.33	4.278%	$127.5633	$127.56	$127.55	$127.60
Purchase #7	$220.44	8.258%	$238.6439	$238.64	$238.65	$238.60
7 purchase totals =	$1,074.38		$1,165.1491	$1,165.14	$1,165.15	$1,165.10