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	$74.94	11.480%	$83.5431	$83.54	$83.55	$83.50
Purchase #2	$77.35	6.415%	$82.312	$82.31	$82.30	$82.30
Purchase #3	$239.97	6.870%	$256.4559	$256.46	$256.45	$256.50
Purchase #4	$64.65	11.709%	$72.2199	$72.22	$72.20	$72.20
Purchase #5	$182.89	13.729%	$207.999	$208.00	$208.00	$208.00
Purchase #6	$35.77	6.119%	$37.9588	$37.96	$37.95	$38.00
Purchase #7	$168.25	12.229%	$188.8253	$188.83	$188.85	$188.80
7 purchase totals =	$843.82		$929.3140	$929.32	$929.30	$929.30