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	$65.40	7.301%	$70.1749	$70.17	$70.15	$70.20
Purchase #2	$232.32	4.568%	$242.9324	$242.93	$242.95	$242.90
Purchase #3	$245.56	4.202%	$255.8784	$255.88	$255.90	$255.90
Purchase #4	$183.28	7.333%	$196.7199	$196.72	$196.70	$196.70
Purchase #5	$145.52	4.365%	$151.8719	$151.87	$151.85	$151.90
Purchase #6	$248.79	11.859%	$278.294	$278.29	$278.30	$278.30
Purchase #7	$227.64	10.655%	$251.895	$251.90	$251.90	$251.90
7 purchase totals =	$1,348.51		$1,447.7665	$1,447.76	$1,447.75	$1,447.80