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	$95.77	10.288%	$105.6228	$105.62	$105.60	$105.60
Purchase #2	$235.61	13.498%	$267.4126	$267.41	$267.40	$267.40
Purchase #3	$246.33	3.609%	$255.22	$255.22	$255.20	$255.20
Purchase #4	$223.63	8.203%	$241.9744	$241.97	$241.95	$242.00
Purchase #5	$65.95	9.560%	$72.2548	$72.25	$72.25	$72.30
Purchase #6	$119.32	8.389%	$129.3298	$129.33	$129.35	$129.30
Purchase #7	$32.91	10.536%	$36.3774	$36.38	$36.40	$36.40
7 purchase totals =	$1,019.52		$1,108.1918	$1,108.18	$1,108.15	$1,108.20