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	$78.89	8.333%	$85.4639	$85.46	$85.45	$85.50
Purchase #2	$83.80	12.339%	$94.1401	$94.14	$94.15	$94.10
Purchase #3	$142.91	6.815%	$152.6493	$152.65	$152.65	$152.60
Purchase #4	$168.29	10.182%	$185.4253	$185.43	$185.45	$185.40
Purchase #5	$157.49	3.327%	$162.7297	$162.73	$162.75	$162.70
Purchase #6	$243.75	10.552%	$269.4705	$269.47	$269.45	$269.50
Purchase #7	$139.26	9.717%	$152.7919	$152.79	$152.80	$152.80
7 purchase totals =	$1,014.39		$1,102.6707	$1,102.67	$1,102.70	$1,102.60