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	$228.72	11.304%	$254.5745	$254.57	$254.55	$254.60
Purchase #2	$103.47	7.364%	$111.0895	$111.09	$111.10	$111.10
Purchase #3	$173.70	6.760%	$185.4421	$185.44	$185.45	$185.40
Purchase #4	$50.93	5.573%	$53.7683	$53.77	$53.75	$53.80
Purchase #5	$123.30	3.813%	$128.0014	$128.00	$128.00	$128.00
Purchase #6	$177.38	4.287%	$184.9843	$184.98	$185.00	$185.00
Purchase #7	$30.50	4.221%	$31.7874	$31.79	$31.80	$31.80
7 purchase totals =	$888.00		$949.6475	$949.64	$949.65	$949.70