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	$233.72	9.502%	$255.9281	$255.93	$255.95	$255.90
Purchase #2	$111.29	11.688%	$124.2976	$124.30	$124.30	$124.30
Purchase #3	$218.48	11.551%	$243.7166	$243.72	$243.70	$243.70
Purchase #4	$104.97	5.414%	$110.6531	$110.65	$110.65	$110.70
Purchase #5	$188.84	12.211%	$211.8993	$211.90	$211.90	$211.90
Purchase #6	$149.73	6.861%	$160.003	$160.00	$160.00	$160.00
Purchase #7	$185.79	4.155%	$193.5096	$193.51	$193.50	$193.50
7 purchase totals =	$1,192.82		$1,300.0073	$1,300.01	$1,300.00	$1,300.00