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	$50.70	11.194%	$56.3754	$56.38	$56.40	$56.40
Purchase #2	$193.89	7.338%	$208.1176	$208.12	$208.10	$208.10
Purchase #3	$142.77	11.289%	$158.8873	$158.89	$158.90	$158.90
Purchase #4	$206.98	12.249%	$232.333	$232.33	$232.35	$232.30
Purchase #5	$78.88	8.380%	$85.4901	$85.49	$85.50	$85.50
Purchase #6	$104.37	5.553%	$110.1657	$110.17	$110.15	$110.20
Purchase #7	$191.38	6.345%	$203.5231	$203.52	$203.50	$203.50
7 purchase totals =	$968.97		$1,054.8922	$1,054.90	$1,054.90	$1,054.90