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	$171.50	8.145%	$185.4687	$185.47	$185.45	$185.50
Purchase #2	$18.36	10.435%	$20.2759	$20.28	$20.30	$20.30
Purchase #3	$228.50	8.819%	$248.6514	$248.65	$248.65	$248.70
Purchase #4	$39.83	5.401%	$41.9812	$41.98	$42.00	$42.00
Purchase #5	$167.69	10.343%	$185.0342	$185.03	$185.05	$185.00
Purchase #6	$187.88	11.206%	$208.9338	$208.93	$208.95	$208.90
Purchase #7	$58.51	4.325%	$61.0406	$61.04	$61.05	$61.00
7 purchase totals =	$872.27		$951.3858	$951.38	$951.45	$951.40