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	$178.55	12.406%	$200.7009	$200.70	$200.70	$200.70
Purchase #2	$71.89	9.769%	$78.9129	$78.91	$78.90	$78.90
Purchase #3	$68.55	13.335%	$77.6911	$77.69	$77.70	$77.70
Purchase #4	$145.95	13.855%	$166.1714	$166.17	$166.15	$166.20
Purchase #5	$221.80	10.854%	$245.8742	$245.87	$245.85	$245.90
Purchase #6	$162.86	7.248%	$174.6641	$174.66	$174.65	$174.70
Purchase #7	$200.64	11.628%	$223.9704	$223.97	$223.95	$224.00
7 purchase totals =	$1,050.24		$1,167.9850	$1,167.97	$1,167.90	$1,168.10