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	$146.39	13.841%	$166.6518	$166.65	$166.65	$166.70
Purchase #2	$62.97	4.343%	$65.7048	$65.70	$65.70	$65.70
Purchase #3	$91.71	8.204%	$99.2339	$99.23	$99.25	$99.20
Purchase #4	$147.35	3.557%	$152.5912	$152.59	$152.60	$152.60
Purchase #5	$32.70	3.524%	$33.8523	$33.85	$33.85	$33.90
Purchase #6	$99.31	9.152%	$108.3989	$108.40	$108.40	$108.40
Purchase #7	$80.79	6.229%	$85.8224	$85.82	$85.80	$85.80
7 purchase totals =	$661.22		$712.2553	$712.24	$712.25	$712.30