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	$219.58	7.761%	$236.6216	$236.62	$236.60	$236.60
Purchase #2	$51.52	5.701%	$54.4572	$54.46	$54.45	$54.50
Purchase #3	$39.31	5.249%	$41.3734	$41.37	$41.35	$41.40
Purchase #4	$17.50	11.612%	$19.5321	$19.53	$19.55	$19.50
Purchase #5	$149.42	3.357%	$154.436	$154.44	$154.45	$154.40
Purchase #6	$85.51	4.718%	$89.5444	$89.54	$89.55	$89.50
Purchase #7	$149.56	3.832%	$155.2911	$155.29	$155.30	$155.30
7 purchase totals =	$712.40		$751.2558	$751.25	$751.25	$751.20