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	$49.66	5.223%	$52.2537	$52.25	$52.25	$52.30
Purchase #2	$225.84	12.407%	$253.86	$253.86	$253.85	$253.90
Purchase #3	$211.25	12.485%	$237.6246	$237.62	$237.60	$237.60
Purchase #4	$229.81	13.495%	$260.8229	$260.82	$260.80	$260.80
Purchase #5	$200.98	7.138%	$215.326	$215.33	$215.35	$215.30
Purchase #6	$100.94	9.473%	$110.502	$110.50	$110.50	$110.50
Purchase #7	$173.33	13.250%	$196.2962	$196.30	$196.30	$196.30
7 purchase totals =	$1,191.81		$1,326.6854	$1,326.68	$1,326.65	$1,326.70