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	$46.34	12.687%	$52.2192	$52.22	$52.20	$52.20
Purchase #2	$75.79	4.851%	$79.4666	$79.47	$79.45	$79.50
Purchase #3	$99.43	12.473%	$111.8319	$111.83	$111.85	$111.80
Purchase #4	$59.61	13.607%	$67.7211	$67.72	$67.70	$67.70
Purchase #5	$107.34	7.444%	$115.3304	$115.33	$115.35	$115.30
Purchase #6	$245.92	6.303%	$261.4203	$261.42	$261.40	$261.40
Purchase #7	$230.79	6.814%	$246.516	$246.52	$246.50	$246.50
7 purchase totals =	$865.22		$934.5055	$934.51	$934.45	$934.40