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	$146.45	12.511%	$164.7724	$164.77	$164.75	$164.80
Purchase #2	$76.85	7.658%	$82.7352	$82.74	$82.75	$82.70
Purchase #3	$245.67	5.546%	$259.2949	$259.29	$259.30	$259.30
Purchase #4	$188.92	9.198%	$206.2969	$206.30	$206.30	$206.30
Purchase #5	$39.98	13.447%	$45.3561	$45.36	$45.35	$45.40
Purchase #6	$203.30	12.684%	$229.0866	$229.09	$229.10	$229.10
Purchase #7	$143.72	11.523%	$160.2809	$160.28	$160.30	$160.30
7 purchase totals =	$1,044.89		$1,147.8230	$1,147.83	$1,147.85	$1,147.90