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	$174.53	5.775%	$184.6091	$184.61	$184.60	$184.60
Purchase #2	$231.86	13.559%	$263.2979	$263.30	$263.30	$263.30
Purchase #3	$152.45	13.322%	$172.7594	$172.76	$172.75	$172.80
Purchase #4	$164.63	4.815%	$172.5569	$172.56	$172.55	$172.60
Purchase #5	$215.32	13.255%	$243.8607	$243.86	$243.85	$243.90
Purchase #6	$110.26	7.220%	$118.2208	$118.22	$118.20	$118.20
Purchase #7	$221.81	12.323%	$249.1436	$249.14	$249.15	$249.10
7 purchase totals =	$1,270.86		$1,404.4484	$1,404.45	$1,404.40	$1,404.50