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	$180.89	7.748%	$194.9054	$194.91	$194.90	$194.90
Purchase #2	$88.81	6.393%	$94.4876	$94.49	$94.50	$94.50
Purchase #3	$101.53	4.753%	$106.3557	$106.36	$106.35	$106.40
Purchase #4	$170.82	8.329%	$185.0476	$185.05	$185.05	$185.00
Purchase #5	$35.72	4.849%	$37.4521	$37.45	$37.45	$37.50
Purchase #6	$45.68	8.126%	$49.392	$49.39	$49.40	$49.40
Purchase #7	$67.92	5.423%	$71.6033	$71.60	$71.60	$71.60
7 purchase totals =	$691.37		$739.2437	$739.25	$739.25	$739.30