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	$71.83	9.267%	$78.4865	$78.49	$78.50	$78.50
Purchase #2	$193.59	10.208%	$213.3517	$213.35	$213.35	$213.40
Purchase #3	$201.80	9.678%	$221.3302	$221.33	$221.35	$221.30
Purchase #4	$54.80	8.201%	$59.2941	$59.29	$59.30	$59.30
Purchase #5	$232.55	7.654%	$250.3494	$250.35	$250.35	$250.30
Purchase #6	$57.32	6.335%	$60.9512	$60.95	$60.95	$61.00
Purchase #7	$122.66	6.815%	$131.0193	$131.02	$131.00	$131.00
7 purchase totals =	$934.55		$1,014.7824	$1,014.78	$1,014.80	$1,014.80