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	$197.31	7.390%	$211.8912	$211.89	$211.90	$211.90
Purchase #2	$28.91	6.700%	$30.847	$30.85	$30.85	$30.80
Purchase #3	$194.90	9.190%	$212.8113	$212.81	$212.80	$212.80
Purchase #4	$175.27	12.107%	$196.4899	$196.49	$196.50	$196.50
Purchase #5	$148.62	12.106%	$166.6119	$166.61	$166.60	$166.60
Purchase #6	$67.90	7.537%	$73.0176	$73.02	$73.00	$73.00
Purchase #7	$31.26	3.843%	$32.4613	$32.46	$32.45	$32.50
7 purchase totals =	$844.17		$924.1302	$924.13	$924.10	$924.10