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	$62.56	12.707%	$70.5095	$70.51	$70.50	$70.50
Purchase #2	$172.73	7.355%	$185.4343	$185.43	$185.45	$185.40
Purchase #3	$193.26	9.350%	$211.3298	$211.33	$211.35	$211.30
Purchase #4	$204.50	8.564%	$222.0134	$222.01	$222.00	$222.00
Purchase #5	$43.77	6.244%	$46.503	$46.50	$46.50	$46.50
Purchase #6	$118.54	9.743%	$130.0894	$130.09	$130.10	$130.10
Purchase #7	$142.28	3.755%	$147.6226	$147.62	$147.60	$147.60
7 purchase totals =	$937.64		$1,013.5020	$1,013.49	$1,013.50	$1,013.40