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	$127.26	3.257%	$131.4049	$131.40	$131.40	$131.40
Purchase #2	$181.90	4.381%	$189.869	$189.87	$189.85	$189.90
Purchase #3	$163.31	5.426%	$172.1712	$172.17	$172.15	$172.20
Purchase #4	$169.83	8.674%	$184.5611	$184.56	$184.55	$184.60
Purchase #5	$212.86	13.107%	$240.7596	$240.76	$240.75	$240.80
Purchase #6	$62.52	10.240%	$68.922	$68.92	$68.90	$68.90
Purchase #7	$175.58	6.810%	$187.537	$187.54	$187.55	$187.50
7 purchase totals =	$1,093.26		$1,175.2248	$1,175.22	$1,175.15	$1,175.30