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	$150.35	11.835%	$168.1439	$168.14	$168.15	$168.10
Purchase #2	$215.36	7.685%	$231.9104	$231.91	$231.90	$231.90
Purchase #3	$243.32	7.481%	$261.5228	$261.52	$261.50	$261.50
Purchase #4	$77.43	7.362%	$83.1304	$83.13	$83.15	$83.10
Purchase #5	$26.70	11.309%	$29.7195	$29.72	$29.70	$29.70
Purchase #6	$41.68	4.811%	$43.6852	$43.69	$43.70	$43.70
Purchase #7	$196.89	6.814%	$210.3061	$210.31	$210.30	$210.30
7 purchase totals =	$951.73		$1,028.4183	$1,028.42	$1,028.40	$1,028.30