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	$30.74	6.563%	$32.7575	$32.76	$32.75	$32.80
Purchase #2	$61.43	6.526%	$65.4389	$65.44	$65.45	$65.40
Purchase #3	$89.32	7.498%	$96.0172	$96.02	$96.00	$96.00
Purchase #4	$40.36	12.366%	$45.3509	$45.35	$45.35	$45.40
Purchase #5	$160.68	7.545%	$172.8033	$172.80	$172.80	$172.80
Purchase #6	$47.35	13.124%	$53.5642	$53.56	$53.55	$53.60
Purchase #7	$22.96	6.621%	$24.4802	$24.48	$24.50	$24.50
7 purchase totals =	$452.84		$490.4122	$490.41	$490.40	$490.50