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	$224.92	6.181%	$238.8223	$238.82	$238.80	$238.80
Purchase #2	$94.88	5.873%	$100.4523	$100.45	$100.45	$100.50
Purchase #3	$161.33	12.859%	$182.0754	$182.08	$182.10	$182.10
Purchase #4	$197.51	7.477%	$212.2778	$212.28	$212.30	$212.30
Purchase #5	$24.41	11.350%	$27.1805	$27.18	$27.20	$27.20
Purchase #6	$58.73	13.735%	$66.7966	$66.80	$66.80	$66.80
Purchase #7	$163.67	6.646%	$174.5475	$174.55	$174.55	$174.50
7 purchase totals =	$925.45		$1,002.1524	$1,002.16	$1,002.20	$1,002.20