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	$105.85	5.370%	$111.5341	$111.53	$111.55	$111.50
Purchase #2	$198.47	11.304%	$220.905	$220.91	$220.90	$220.90
Purchase #3	$250.48	6.345%	$266.373	$266.37	$266.35	$266.40
Purchase #4	$156.96	5.835%	$166.1186	$166.12	$166.10	$166.10
Purchase #5	$56.80	4.619%	$59.4236	$59.42	$59.40	$59.40
Purchase #6	$216.59	3.217%	$223.5577	$223.56	$223.55	$223.60
Purchase #7	$94.58	8.704%	$102.8122	$102.81	$102.80	$102.80
7 purchase totals =	$1,079.73		$1,150.7242	$1,150.72	$1,150.65	$1,150.70