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	$152.79	4.536%	$159.7206	$159.72	$159.70	$159.70
Purchase #2	$237.61	10.788%	$263.2434	$263.24	$263.25	$263.20
Purchase #3	$80.76	7.424%	$86.7556	$86.76	$86.75	$86.80
Purchase #4	$151.55	11.237%	$168.5797	$168.58	$168.60	$168.60
Purchase #5	$153.48	4.806%	$160.8562	$160.86	$160.85	$160.90
Purchase #6	$25.27	13.417%	$28.6605	$28.66	$28.65	$28.70
Purchase #7	$221.85	5.168%	$233.3152	$233.32	$233.30	$233.30
7 purchase totals =	$1,023.31		$1,101.1312	$1,101.14	$1,101.10	$1,101.20