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	$41.50	11.162%	$46.1322	$46.13	$46.15	$46.10
Purchase #2	$180.89	10.740%	$200.3176	$200.32	$200.30	$200.30
Purchase #3	$8.90	7.173%	$9.5384	$9.54	$9.55	$9.50
Purchase #4	$38.28	4.648%	$40.0593	$40.06	$40.05	$40.10
Purchase #5	$93.87	6.397%	$99.8749	$99.87	$99.85	$99.90
Purchase #6	$21.97	4.203%	$22.8934	$22.89	$22.90	$22.90
Purchase #7	$33.52	10.613%	$37.0775	$37.08	$37.10	$37.10
7 purchase totals =	$418.93		$455.8933	$455.89	$455.90	$455.90