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	$59.64	3.721%	$61.8592	$61.86	$61.85	$61.90
Purchase #2	$92.43	8.759%	$100.5259	$100.53	$100.55	$100.50
Purchase #3	$205.70	8.269%	$222.7093	$222.71	$222.70	$222.70
Purchase #4	$158.66	3.439%	$164.1163	$164.12	$164.10	$164.10
Purchase #5	$19.52	9.356%	$21.3463	$21.35	$21.35	$21.30
Purchase #6	$109.39	12.281%	$122.8242	$122.82	$122.80	$122.80
Purchase #7	$47.39	12.289%	$53.2138	$53.21	$53.20	$53.20
7 purchase totals =	$692.73		$746.5950	$746.60	$746.55	$746.50