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	$43.78	12.200%	$49.1212	$49.12	$49.10	$49.10
Purchase #2	$88.44	9.417%	$96.7684	$96.77	$96.75	$96.80
Purchase #3	$44.76	7.773%	$48.2392	$48.24	$48.25	$48.20
Purchase #4	$76.31	8.186%	$82.5567	$82.56	$82.55	$82.60
Purchase #5	$52.93	4.624%	$55.3775	$55.38	$55.40	$55.40
Purchase #6	$52.97	12.651%	$59.6712	$59.67	$59.65	$59.70
Purchase #7	$89.57	4.513%	$93.6123	$93.61	$93.60	$93.60
7 purchase totals =	$448.76		$485.3465	$485.35	$485.30	$485.40