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	$31.72	10.848%	$35.161	$35.16	$35.15	$35.20
Purchase #2	$101.35	3.275%	$104.6692	$104.67	$104.65	$104.70
Purchase #3	$99.61	8.822%	$108.3976	$108.40	$108.40	$108.40
Purchase #4	$89.34	11.872%	$99.9464	$99.95	$99.95	$99.90
Purchase #5	$27.96	3.283%	$28.8779	$28.88	$28.90	$28.90
Purchase #6	$233.57	10.700%	$258.562	$258.56	$258.55	$258.60
Purchase #7	$246.67	4.799%	$258.5077	$258.51	$258.50	$258.50
7 purchase totals =	$830.22		$894.1218	$894.13	$894.10	$894.20