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	$198.65	13.550%	$225.5671	$225.57	$225.55	$225.60
Purchase #2	$83.82	6.578%	$89.3337	$89.33	$89.35	$89.30
Purchase #3	$155.53	11.120%	$172.8249	$172.82	$172.80	$172.80
Purchase #4	$127.38	4.612%	$133.2548	$133.25	$133.25	$133.30
Purchase #5	$86.71	4.630%	$90.7247	$90.72	$90.70	$90.70
Purchase #6	$113.79	5.639%	$120.2066	$120.21	$120.20	$120.20
Purchase #7	$196.71	5.254%	$207.0451	$207.05	$207.05	$207.00
7 purchase totals =	$962.59		$1,038.9569	$1,038.95	$1,038.90	$1,038.90