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	$92.86	7.586%	$99.9044	$99.90	$99.90	$99.90
Purchase #2	$53.51	7.791%	$57.679	$57.68	$57.70	$57.70
Purchase #3	$11.54	8.385%	$12.5076	$12.51	$12.50	$12.50
Purchase #4	$46.37	9.605%	$50.8238	$50.82	$50.80	$50.80
Purchase #5	$144.93	12.368%	$162.8549	$162.85	$162.85	$162.90
Purchase #6	$188.27	5.206%	$198.0713	$198.07	$198.05	$198.10
Purchase #7	$201.67	4.590%	$210.9267	$210.93	$210.95	$210.90
7 purchase totals =	$739.15		$792.7677	$792.76	$792.75	$792.80