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	$83.73	10.120%	$92.2035	$92.20	$92.20	$92.20
Purchase #2	$133.49	13.225%	$151.1441	$151.14	$151.15	$151.10
Purchase #3	$32.47	3.472%	$33.5974	$33.60	$33.60	$33.60
Purchase #4	$6.74	10.391%	$7.4404	$7.44	$7.45	$7.40
Purchase #5	$31.56	7.200%	$33.8323	$33.83	$33.85	$33.80
Purchase #6	$134.28	10.158%	$147.9202	$147.92	$147.90	$147.90
Purchase #7	$26.29	13.858%	$29.9333	$29.93	$29.95	$29.90
7 purchase totals =	$448.56		$496.0712	$496.06	$496.10	$495.90