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	$35.41	7.103%	$37.9252	$37.93	$37.95	$37.90
Purchase #2	$74.75	4.528%	$78.1347	$78.13	$78.15	$78.10
Purchase #3	$80.57	6.494%	$85.8022	$85.80	$85.80	$85.80
Purchase #4	$39.96	8.472%	$43.3454	$43.35	$43.35	$43.30
Purchase #5	$172.72	5.262%	$181.8085	$181.81	$181.80	$181.80
Purchase #6	$228.54	5.159%	$240.3304	$240.33	$240.35	$240.30
Purchase #7	$24.65	10.337%	$27.1981	$27.20	$27.20	$27.20
7 purchase totals =	$656.60		$694.5445	$694.55	$694.60	$694.40