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	$183.43	4.636%	$191.9338	$191.93	$191.95	$191.90
Purchase #2	$240.51	6.423%	$255.958	$255.96	$255.95	$256.00
Purchase #3	$31.38	6.797%	$33.5129	$33.51	$33.50	$33.50
Purchase #4	$234.87	3.624%	$243.3817	$243.38	$243.40	$243.40
Purchase #5	$106.79	6.234%	$113.4473	$113.45	$113.45	$113.40
Purchase #6	$218.82	8.257%	$236.888	$236.89	$236.90	$236.90
Purchase #7	$176.69	7.256%	$189.5106	$189.51	$189.50	$189.50
7 purchase totals =	$1,192.49		$1,264.6323	$1,264.63	$1,264.65	$1,264.60