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	$154.79	5.221%	$162.8716	$162.87	$162.85	$162.90
Purchase #2	$200.55	13.321%	$227.2653	$227.27	$227.25	$227.30
Purchase #3	$80.67	6.573%	$85.9724	$85.97	$85.95	$86.00
Purchase #4	$128.33	11.573%	$143.1816	$143.18	$143.20	$143.20
Purchase #5	$41.39	13.186%	$46.8477	$46.85	$46.85	$46.80
Purchase #6	$101.54	9.740%	$111.43	$111.43	$111.45	$111.40
Purchase #7	$233.74	9.589%	$256.1533	$256.15	$256.15	$256.20
7 purchase totals =	$941.01		$1,033.7219	$1,033.72	$1,033.70	$1,033.80