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	$33.36	12.217%	$37.4356	$37.44	$37.45	$37.40
Purchase #2	$215.90	13.579%	$245.2171	$245.22	$245.20	$245.20
Purchase #3	$38.97	7.865%	$42.035	$42.04	$42.05	$42.00
Purchase #4	$38.43	10.372%	$42.416	$42.42	$42.40	$42.40
Purchase #5	$37.97	6.192%	$40.3211	$40.32	$40.30	$40.30
Purchase #6	$28.76	10.741%	$31.8491	$31.85	$31.85	$31.80
Purchase #7	$214.95	10.200%	$236.8749	$236.87	$236.85	$236.90
7 purchase totals =	$608.34		$676.1488	$676.16	$676.10	$676.00