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	$143.62	8.797%	$156.2543	$156.25	$156.25	$156.30
Purchase #2	$193.34	8.859%	$210.468	$210.47	$210.45	$210.50
Purchase #3	$111.75	4.400%	$116.667	$116.67	$116.65	$116.70
Purchase #4	$67.33	7.672%	$72.4956	$72.50	$72.50	$72.50
Purchase #5	$73.84	10.417%	$81.5319	$81.53	$81.55	$81.50
Purchase #6	$215.64	7.719%	$232.2853	$232.29	$232.30	$232.30
Purchase #7	$142.73	9.257%	$155.9425	$155.94	$155.95	$155.90
7 purchase totals =	$948.25		$1,025.6446	$1,025.65	$1,025.65	$1,025.70