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	$198.36	12.266%	$222.6908	$222.69	$222.70	$222.70
Purchase #2	$178.41	12.158%	$200.1011	$200.10	$200.10	$200.10
Purchase #3	$97.30	6.525%	$103.6488	$103.65	$103.65	$103.60
Purchase #4	$114.33	13.842%	$130.1556	$130.16	$130.15	$130.20
Purchase #5	$112.93	13.119%	$127.7453	$127.75	$127.75	$127.70
Purchase #6	$5.50	3.507%	$5.6929	$5.69	$5.70	$5.70
Purchase #7	$246.82	13.400%	$279.8939	$279.89	$279.90	$279.90
7 purchase totals =	$953.65		$1,069.9284	$1,069.93	$1,069.95	$1,069.90