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	$172.83	10.729%	$191.3729	$191.37	$191.35	$191.40
Purchase #2	$173.90	13.150%	$196.7679	$196.77	$196.75	$196.80
Purchase #3	$168.91	13.753%	$192.1402	$192.14	$192.15	$192.10
Purchase #4	$147.93	4.813%	$155.0499	$155.05	$155.05	$155.00
Purchase #5	$53.96	10.313%	$59.5249	$59.52	$59.50	$59.50
Purchase #6	$65.62	12.638%	$73.9131	$73.91	$73.90	$73.90
Purchase #7	$238.89	7.852%	$257.6476	$257.65	$257.65	$257.60
7 purchase totals =	$1,022.04		$1,126.4165	$1,126.41	$1,126.35	$1,126.30