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	$11.73	4.579%	$12.2671	$12.27	$12.25	$12.30
Purchase #2	$200.59	11.289%	$223.2346	$223.23	$223.25	$223.20
Purchase #3	$125.90	5.570%	$132.9126	$132.91	$132.90	$132.90
Purchase #4	$182.51	3.861%	$189.5567	$189.56	$189.55	$189.60
Purchase #5	$42.38	8.682%	$46.0594	$46.06	$46.05	$46.10
Purchase #6	$96.70	10.793%	$107.1368	$107.14	$107.15	$107.10
Purchase #7	$31.41	4.800%	$32.9177	$32.92	$32.90	$32.90
7 purchase totals =	$691.22		$744.0849	$744.09	$744.05	$744.10