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	$175.35	9.303%	$191.6628	$191.66	$191.65	$191.70
Purchase #2	$100.53	11.335%	$111.9251	$111.93	$111.95	$111.90
Purchase #3	$97.96	3.850%	$101.7315	$101.73	$101.75	$101.70
Purchase #4	$89.27	5.439%	$94.1254	$94.13	$94.15	$94.10
Purchase #5	$8.86	13.712%	$10.0749	$10.07	$10.05	$10.10
Purchase #6	$246.78	13.530%	$280.1693	$280.17	$280.15	$280.20
Purchase #7	$240.94	8.490%	$261.3958	$261.40	$261.40	$261.40
7 purchase totals =	$959.69		$1,051.0848	$1,051.09	$1,051.10	$1,051.10