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	$201.84	10.211%	$222.4499	$222.45	$222.45	$222.40
Purchase #2	$32.75	9.641%	$35.9074	$35.91	$35.90	$35.90
Purchase #3	$148.36	13.564%	$168.4836	$168.48	$168.50	$168.50
Purchase #4	$249.52	3.502%	$258.2582	$258.26	$258.25	$258.30
Purchase #5	$229.72	6.515%	$244.6863	$244.69	$244.70	$244.70
Purchase #6	$92.96	7.726%	$100.1421	$100.14	$100.15	$100.10
Purchase #7	$91.54	3.463%	$94.71	$94.71	$94.70	$94.70
7 purchase totals =	$1,046.69		$1,124.6375	$1,124.64	$1,124.65	$1,124.60