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	$54.87	11.666%	$61.2711	$61.27	$61.25	$61.30
Purchase #2	$118.67	5.325%	$124.9892	$124.99	$125.00	$125.00
Purchase #3	$117.85	13.607%	$133.8858	$133.89	$133.90	$133.90
Purchase #4	$196.49	13.550%	$223.1144	$223.11	$223.10	$223.10
Purchase #5	$173.88	4.125%	$181.0526	$181.05	$181.05	$181.10
Purchase #6	$162.72	4.362%	$169.8178	$169.82	$169.80	$169.80
Purchase #7	$179.39	8.228%	$194.1502	$194.15	$194.15	$194.20
7 purchase totals =	$1,003.87		$1,088.2811	$1,088.28	$1,088.25	$1,088.40