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	$193.66	8.561%	$210.2392	$210.24	$210.25	$210.20
Purchase #2	$158.54	3.581%	$164.2173	$164.22	$164.20	$164.20
Purchase #3	$46.91	10.178%	$51.6845	$51.68	$51.70	$51.70
Purchase #4	$139.59	9.398%	$152.7087	$152.71	$152.70	$152.70
Purchase #5	$148.38	11.143%	$164.914	$164.91	$164.90	$164.90
Purchase #6	$37.38	13.102%	$42.2775	$42.28	$42.30	$42.30
Purchase #7	$21.73	4.633%	$22.7368	$22.74	$22.75	$22.70
7 purchase totals =	$746.19		$808.7780	$808.78	$808.80	$808.70