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	$194.69	10.379%	$214.8969	$214.90	$214.90	$214.90
Purchase #2	$134.60	13.215%	$152.3874	$152.39	$152.40	$152.40
Purchase #3	$110.72	8.274%	$119.881	$119.88	$119.90	$119.90
Purchase #4	$228.48	4.772%	$239.3831	$239.38	$239.40	$239.40
Purchase #5	$29.91	13.170%	$33.8491	$33.85	$33.85	$33.80
Purchase #6	$158.80	4.766%	$166.3684	$166.37	$166.35	$166.40
Purchase #7	$92.70	4.441%	$96.8168	$96.82	$96.80	$96.80
7 purchase totals =	$949.90		$1,023.5827	$1,023.59	$1,023.60	$1,023.60