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	$59.67	9.466%	$65.3184	$65.32	$65.30	$65.30
Purchase #2	$136.27	7.273%	$146.1809	$146.18	$146.20	$146.20
Purchase #3	$162.87	10.829%	$180.5072	$180.51	$180.50	$180.50
Purchase #4	$169.54	3.220%	$174.9992	$175.00	$175.00	$175.00
Purchase #5	$237.50	10.767%	$263.0716	$263.07	$263.05	$263.10
Purchase #6	$128.46	9.811%	$141.0632	$141.06	$141.05	$141.10
Purchase #7	$109.57	12.778%	$123.5709	$123.57	$123.55	$123.60
7 purchase totals =	$1,003.88		$1,094.7114	$1,094.71	$1,094.65	$1,094.80