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	$85.52	3.561%	$88.5654	$88.57	$88.55	$88.60
Purchase #2	$216.52	7.220%	$232.1527	$232.15	$232.15	$232.20
Purchase #3	$151.28	12.359%	$169.9767	$169.98	$170.00	$170.00
Purchase #4	$116.33	7.110%	$124.6011	$124.60	$124.60	$124.60
Purchase #5	$151.25	10.548%	$167.2039	$167.20	$167.20	$167.20
Purchase #6	$80.68	11.260%	$89.7646	$89.76	$89.75	$89.80
Purchase #7	$134.98	13.798%	$153.6045	$153.60	$153.60	$153.60
7 purchase totals =	$936.56		$1,025.8689	$1,025.86	$1,025.85	$1,026.00