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	$132.30	7.687%	$142.4699	$142.47	$142.45	$142.50
Purchase #2	$24.67	3.530%	$25.5409	$25.54	$25.55	$25.50
Purchase #3	$33.72	11.399%	$37.5637	$37.56	$37.55	$37.60
Purchase #4	$116.36	10.749%	$128.8675	$128.87	$128.85	$128.90
Purchase #5	$210.68	13.505%	$239.1323	$239.13	$239.15	$239.10
Purchase #6	$188.46	9.251%	$205.8944	$205.89	$205.90	$205.90
Purchase #7	$93.72	8.710%	$101.883	$101.88	$101.90	$101.90
7 purchase totals =	$799.91		$881.3517	$881.34	$881.35	$881.40