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	$181.88	8.263%	$196.9087	$196.91	$196.90	$196.90
Purchase #2	$240.73	9.702%	$264.0856	$264.09	$264.10	$264.10
Purchase #3	$217.81	4.281%	$227.1344	$227.13	$227.15	$227.10
Purchase #4	$143.80	11.306%	$160.058	$160.06	$160.05	$160.10
Purchase #5	$32.30	9.490%	$35.3653	$35.37	$35.35	$35.40
Purchase #6	$186.70	13.402%	$211.7215	$211.72	$211.70	$211.70
Purchase #7	$65.83	11.701%	$73.5328	$73.53	$73.55	$73.50
7 purchase totals =	$1,069.05		$1,168.8063	$1,168.81	$1,168.80	$1,168.80