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	$174.59	6.210%	$185.432	$185.43	$185.45	$185.40
Purchase #2	$49.85	11.161%	$55.4138	$55.41	$55.40	$55.40
Purchase #3	$74.85	6.251%	$79.5289	$79.53	$79.55	$79.50
Purchase #4	$245.76	3.186%	$253.5899	$253.59	$253.60	$253.60
Purchase #5	$73.65	6.561%	$78.4822	$78.48	$78.50	$78.50
Purchase #6	$199.69	8.750%	$217.1629	$217.16	$217.15	$217.20
Purchase #7	$230.34	5.352%	$242.6678	$242.67	$242.65	$242.70
7 purchase totals =	$1,048.73		$1,112.2775	$1,112.27	$1,112.30	$1,112.30