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	$220.30	8.102%	$238.1487	$238.15	$238.15	$238.10
Purchase #2	$11.98	10.661%	$13.2572	$13.26	$13.25	$13.30
Purchase #3	$174.77	8.862%	$190.2581	$190.26	$190.25	$190.30
Purchase #4	$116.50	5.414%	$122.8073	$122.81	$122.80	$122.80
Purchase #5	$68.28	6.830%	$72.9435	$72.94	$72.95	$72.90
Purchase #6	$235.97	6.289%	$250.8102	$250.81	$250.80	$250.80
Purchase #7	$118.54	8.392%	$128.4879	$128.49	$128.50	$128.50
7 purchase totals =	$946.34		$1,016.7129	$1,016.72	$1,016.70	$1,016.70