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	$195.47	10.579%	$216.1488	$216.15	$216.15	$216.10
Purchase #2	$71.31	8.424%	$77.3172	$77.32	$77.30	$77.30
Purchase #3	$84.44	5.117%	$88.7608	$88.76	$88.75	$88.80
Purchase #4	$78.85	4.828%	$82.6569	$82.66	$82.65	$82.70
Purchase #5	$105.35	6.464%	$112.1598	$112.16	$112.15	$112.20
Purchase #6	$31.52	7.449%	$33.8679	$33.87	$33.85	$33.90
Purchase #7	$217.33	4.511%	$227.1338	$227.13	$227.15	$227.10
7 purchase totals =	$784.27		$838.0452	$838.05	$838.00	$838.10