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	$235.70	3.282%	$243.4357	$243.44	$243.45	$243.40
Purchase #2	$58.69	12.532%	$66.045	$66.05	$66.05	$66.00
Purchase #3	$22.36	9.575%	$24.501	$24.50	$24.50	$24.50
Purchase #4	$135.30	5.382%	$142.5818	$142.58	$142.60	$142.60
Purchase #5	$247.59	9.644%	$271.4676	$271.47	$271.45	$271.50
Purchase #6	$131.63	5.814%	$139.283	$139.28	$139.30	$139.30
Purchase #7	$240.59	10.796%	$266.5641	$266.56	$266.55	$266.60
7 purchase totals =	$1,071.86		$1,153.8782	$1,153.88	$1,153.90	$1,153.90