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	$92.95	10.865%	$103.049	$103.05	$103.05	$103.00
Purchase #2	$130.40	13.836%	$148.4421	$148.44	$148.45	$148.40
Purchase #3	$180.94	8.213%	$195.8006	$195.80	$195.80	$195.80
Purchase #4	$33.91	13.349%	$38.4366	$38.44	$38.45	$38.40
Purchase #5	$128.48	10.266%	$141.6698	$141.67	$141.65	$141.70
Purchase #6	$61.33	4.599%	$64.1506	$64.15	$64.15	$64.20
Purchase #7	$85.27	5.413%	$89.8857	$89.89	$89.90	$89.90
7 purchase totals =	$713.28		$781.4344	$781.44	$781.45	$781.40