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	$77.97	5.672%	$82.3925	$82.39	$82.40	$82.40
Purchase #2	$136.98	11.762%	$153.0916	$153.09	$153.10	$153.10
Purchase #3	$234.85	4.708%	$245.9067	$245.91	$245.90	$245.90
Purchase #4	$169.77	9.292%	$185.545	$185.55	$185.55	$185.50
Purchase #5	$208.26	13.542%	$236.4626	$236.46	$236.45	$236.50
Purchase #6	$105.39	5.462%	$111.1464	$111.15	$111.15	$111.10
Purchase #7	$55.73	4.273%	$58.1113	$58.11	$58.10	$58.10
7 purchase totals =	$988.95		$1,072.6561	$1,072.66	$1,072.65	$1,072.60