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	$47.67	12.170%	$53.4714	$53.47	$53.45	$53.50
Purchase #2	$214.52	6.460%	$228.378	$228.38	$228.40	$228.40
Purchase #3	$129.33	11.687%	$144.4448	$144.44	$144.45	$144.40
Purchase #4	$234.47	12.367%	$263.4669	$263.47	$263.45	$263.50
Purchase #5	$238.33	13.267%	$269.9492	$269.95	$269.95	$269.90
Purchase #6	$41.47	6.686%	$44.2427	$44.24	$44.25	$44.20
Purchase #7	$85.67	7.192%	$91.8314	$91.83	$91.85	$91.80
7 purchase totals =	$991.46		$1,095.7844	$1,095.78	$1,095.80	$1,095.70