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	$179.56	11.430%	$200.0837	$200.08	$200.10	$200.10
Purchase #2	$230.38	12.300%	$258.7167	$258.72	$258.70	$258.70
Purchase #3	$94.81	7.511%	$101.9312	$101.93	$101.95	$101.90
Purchase #4	$132.40	9.800%	$145.3752	$145.38	$145.40	$145.40
Purchase #5	$221.96	5.555%	$234.2899	$234.29	$234.30	$234.30
Purchase #6	$158.64	9.784%	$174.1613	$174.16	$174.15	$174.20
Purchase #7	$28.66	10.278%	$31.6057	$31.61	$31.60	$31.60
7 purchase totals =	$1,046.41		$1,146.1637	$1,146.17	$1,146.20	$1,146.20