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	$229.61	11.179%	$255.2781	$255.28	$255.30	$255.30
Purchase #2	$43.33	13.297%	$49.0916	$49.09	$49.10	$49.10
Purchase #3	$29.56	12.630%	$33.2934	$33.29	$33.30	$33.30
Purchase #4	$148.64	11.653%	$165.961	$165.96	$165.95	$166.00
Purchase #5	$88.79	5.484%	$93.6592	$93.66	$93.65	$93.70
Purchase #6	$159.74	10.674%	$176.7906	$176.79	$176.80	$176.80
Purchase #7	$158.56	6.143%	$168.3003	$168.30	$168.30	$168.30
7 purchase totals =	$858.23		$942.3742	$942.37	$942.40	$942.50