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	$20.66	7.192%	$22.1459	$22.15	$22.15	$22.10
Purchase #2	$167.41	13.793%	$190.5009	$190.50	$190.50	$190.50
Purchase #3	$185.94	13.832%	$211.6592	$211.66	$211.65	$211.70
Purchase #4	$140.76	8.139%	$152.2165	$152.22	$152.20	$152.20
Purchase #5	$148.40	6.594%	$158.1855	$158.19	$158.20	$158.20
Purchase #6	$44.97	13.521%	$51.0504	$51.05	$51.05	$51.10
Purchase #7	$195.55	11.755%	$218.5369	$218.54	$218.55	$218.50
7 purchase totals =	$903.69		$1,004.2953	$1,004.31	$1,004.30	$1,004.30