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	$199.57	4.767%	$209.0835	$209.08	$209.10	$209.10
Purchase #2	$204.84	6.488%	$218.13	$218.13	$218.15	$218.10
Purchase #3	$39.75	5.653%	$41.9971	$42.00	$42.00	$42.00
Purchase #4	$26.72	9.650%	$29.2985	$29.30	$29.30	$29.30
Purchase #5	$234.45	11.123%	$260.5279	$260.53	$260.55	$260.50
Purchase #6	$117.67	8.380%	$127.5307	$127.53	$127.55	$127.50
Purchase #7	$243.25	13.271%	$275.5317	$275.53	$275.55	$275.50
7 purchase totals =	$1,066.25		$1,162.0994	$1,162.10	$1,162.20	$1,162.00