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	$12.89	11.117%	$14.323	$14.32	$14.30	$14.30
Purchase #2	$88.96	8.836%	$96.8205	$96.82	$96.80	$96.80
Purchase #3	$184.47	6.504%	$196.4679	$196.47	$196.45	$196.50
Purchase #4	$211.65	4.529%	$221.2356	$221.24	$221.25	$221.20
Purchase #5	$190.54	10.770%	$211.0612	$211.06	$211.05	$211.10
Purchase #6	$25.66	10.317%	$28.3073	$28.31	$28.30	$28.30
Purchase #7	$209.46	9.458%	$229.2707	$229.27	$229.25	$229.30
7 purchase totals =	$923.63		$997.4862	$997.49	$997.40	$997.50