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	$205.87	4.708%	$215.5624	$215.56	$215.55	$215.60
Purchase #2	$100.38	8.435%	$108.8471	$108.85	$108.85	$108.80
Purchase #3	$42.56	6.805%	$45.4562	$45.46	$45.45	$45.50
Purchase #4	$100.55	13.561%	$114.1856	$114.19	$114.20	$114.20
Purchase #5	$185.58	8.800%	$201.911	$201.91	$201.90	$201.90
Purchase #6	$250.29	10.174%	$275.7545	$275.75	$275.75	$275.80
Purchase #7	$57.50	5.660%	$60.7545	$60.75	$60.75	$60.80
7 purchase totals =	$942.73		$1,022.4713	$1,022.47	$1,022.45	$1,022.60