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	$56.99	9.580%	$62.4496	$62.45	$62.45	$62.40
Purchase #2	$110.95	7.145%	$118.8774	$118.88	$118.90	$118.90
Purchase #3	$121.55	7.661%	$130.8619	$130.86	$130.85	$130.90
Purchase #4	$200.36	5.253%	$210.8849	$210.88	$210.90	$210.90
Purchase #5	$247.67	12.293%	$278.1161	$278.12	$278.10	$278.10
Purchase #6	$57.72	9.418%	$63.1561	$63.16	$63.15	$63.20
Purchase #7	$146.37	13.769%	$166.5237	$166.52	$166.50	$166.50
7 purchase totals =	$941.61		$1,030.8697	$1,030.87	$1,030.85	$1,030.90