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	$186.49	12.342%	$209.5066	$209.51	$209.50	$209.50
Purchase #2	$125.46	13.684%	$142.6279	$142.63	$142.65	$142.60
Purchase #3	$186.68	7.550%	$200.7743	$200.77	$200.75	$200.80
Purchase #4	$118.39	8.869%	$128.89	$128.89	$128.90	$128.90
Purchase #5	$212.41	5.207%	$223.4702	$223.47	$223.45	$223.50
Purchase #6	$118.98	10.738%	$131.7561	$131.76	$131.75	$131.80
Purchase #7	$135.50	8.320%	$146.7736	$146.77	$146.75	$146.80
7 purchase totals =	$1,083.91		$1,183.7987	$1,183.80	$1,183.75	$1,183.90