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	$173.45	13.516%	$196.8935	$196.89	$196.90	$196.90
Purchase #2	$236.43	4.519%	$247.1143	$247.11	$247.10	$247.10
Purchase #3	$98.39	3.831%	$102.1593	$102.16	$102.15	$102.20
Purchase #4	$63.42	9.787%	$69.6269	$69.63	$69.65	$69.60
Purchase #5	$183.25	11.390%	$204.1222	$204.12	$204.10	$204.10
Purchase #6	$50.42	9.694%	$55.3077	$55.31	$55.30	$55.30
Purchase #7	$92.64	13.847%	$105.4679	$105.47	$105.45	$105.50
7 purchase totals =	$898.00		$980.6918	$980.69	$980.65	$980.70