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	$35.74	3.713%	$37.067	$37.07	$37.05	$37.10
Purchase #2	$140.33	7.696%	$151.1298	$151.13	$151.15	$151.10
Purchase #3	$112.56	5.586%	$118.8476	$118.85	$118.85	$118.80
Purchase #4	$55.90	3.279%	$57.733	$57.73	$57.75	$57.70
Purchase #5	$136.30	5.741%	$144.125	$144.13	$144.15	$144.10
Purchase #6	$96.58	12.763%	$108.9065	$108.91	$108.90	$108.90
Purchase #7	$67.29	5.123%	$70.7373	$70.74	$70.75	$70.70
7 purchase totals =	$644.70		$688.5462	$688.56	$688.60	$688.40