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	$83.25	8.608%	$90.4162	$90.42	$90.40	$90.40
Purchase #2	$173.97	10.546%	$192.3169	$192.32	$192.30	$192.30
Purchase #3	$92.25	7.347%	$99.0276	$99.03	$99.05	$99.00
Purchase #4	$65.46	9.644%	$71.773	$71.77	$71.75	$71.80
Purchase #5	$213.47	3.871%	$221.7334	$221.73	$221.75	$221.70
Purchase #6	$215.82	5.531%	$227.757	$227.76	$227.75	$227.80
Purchase #7	$165.50	6.359%	$176.0241	$176.02	$176.00	$176.00
7 purchase totals =	$1,009.72		$1,079.0482	$1,079.05	$1,079.00	$1,079.00