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	$160.93	9.627%	$176.4227	$176.42	$176.40	$176.40
Purchase #2	$58.48	8.614%	$63.5175	$63.52	$63.50	$63.50
Purchase #3	$43.37	13.319%	$49.1465	$49.15	$49.15	$49.10
Purchase #4	$138.68	9.552%	$151.9267	$151.93	$151.95	$151.90
Purchase #5	$96.51	4.398%	$100.7545	$100.75	$100.75	$100.80
Purchase #6	$111.33	12.379%	$125.1115	$125.11	$125.10	$125.10
Purchase #7	$95.36	4.514%	$99.6646	$99.66	$99.65	$99.70
7 purchase totals =	$704.66		$766.5440	$766.54	$766.50	$766.50