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	$180.28	8.714%	$195.9896	$195.99	$196.00	$196.00
Purchase #2	$190.37	5.222%	$200.3111	$200.31	$200.30	$200.30
Purchase #3	$73.41	6.104%	$77.8909	$77.89	$77.90	$77.90
Purchase #4	$21.51	13.637%	$24.4433	$24.44	$24.45	$24.40
Purchase #5	$244.89	11.483%	$273.0107	$273.01	$273.00	$273.00
Purchase #6	$117.76	11.135%	$130.8726	$130.87	$130.85	$130.90
Purchase #7	$125.72	12.668%	$141.6462	$141.65	$141.65	$141.60
7 purchase totals =	$953.94		$1,044.1644	$1,044.16	$1,044.15	$1,044.10