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	$106.42	13.363%	$120.6409	$120.64	$120.65	$120.60
Purchase #2	$85.29	7.613%	$91.7831	$91.78	$91.80	$91.80
Purchase #3	$149.36	3.205%	$154.147	$154.15	$154.15	$154.10
Purchase #4	$211.61	13.597%	$240.3826	$240.38	$240.40	$240.40
Purchase #5	$233.30	9.252%	$254.8849	$254.88	$254.90	$254.90
Purchase #6	$123.69	3.156%	$127.5937	$127.59	$127.60	$127.60
Purchase #7	$99.60	5.375%	$104.9535	$104.95	$104.95	$105.00
7 purchase totals =	$1,009.27		$1,094.3857	$1,094.37	$1,094.45	$1,094.40