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	$186.99	10.610%	$206.8296	$206.83	$206.85	$206.80
Purchase #2	$132.49	7.561%	$142.5076	$142.51	$142.50	$142.50
Purchase #3	$216.59	13.517%	$245.8665	$245.87	$245.85	$245.90
Purchase #4	$25.92	9.729%	$28.4418	$28.44	$28.45	$28.40
Purchase #5	$47.76	9.606%	$52.3478	$52.35	$52.35	$52.30
Purchase #6	$170.46	11.644%	$190.3084	$190.31	$190.30	$190.30
Purchase #7	$143.87	5.261%	$151.439	$151.44	$151.45	$151.40
7 purchase totals =	$924.08		$1,017.7407	$1,017.75	$1,017.75	$1,017.60