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	$145.27	10.579%	$160.6381	$160.64	$160.65	$160.60
Purchase #2	$144.55	7.770%	$155.7815	$155.78	$155.80	$155.80
Purchase #3	$79.45	12.401%	$89.3026	$89.30	$89.30	$89.30
Purchase #4	$138.85	5.792%	$146.8922	$146.89	$146.90	$146.90
Purchase #5	$229.76	7.849%	$247.7939	$247.79	$247.80	$247.80
Purchase #6	$219.55	9.381%	$240.146	$240.15	$240.15	$240.10
Purchase #7	$211.31	8.364%	$228.984	$228.98	$229.00	$229.00
7 purchase totals =	$1,168.74		$1,269.5383	$1,269.53	$1,269.60	$1,269.50