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	$172.91	12.624%	$194.7382	$194.74	$194.75	$194.70
Purchase #2	$123.38	3.216%	$127.3479	$127.35	$127.35	$127.30
Purchase #3	$41.33	11.758%	$46.1896	$46.19	$46.20	$46.20
Purchase #4	$169.25	9.845%	$185.9127	$185.91	$185.90	$185.90
Purchase #5	$245.76	9.476%	$269.0482	$269.05	$269.05	$269.00
Purchase #6	$112.25	5.434%	$118.3497	$118.35	$118.35	$118.30
Purchase #7	$148.44	13.247%	$168.1038	$168.10	$168.10	$168.10
7 purchase totals =	$1,013.32		$1,109.6901	$1,109.69	$1,109.70	$1,109.50