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	$84.93	7.756%	$91.5172	$91.52	$91.50	$91.50
Purchase #2	$42.94	7.700%	$46.2464	$46.25	$46.25	$46.20
Purchase #3	$132.30	10.374%	$146.0248	$146.02	$146.00	$146.00
Purchase #4	$130.45	5.568%	$137.7135	$137.71	$137.70	$137.70
Purchase #5	$114.83	10.666%	$127.0778	$127.08	$127.10	$127.10
Purchase #6	$103.89	7.657%	$111.8449	$111.84	$111.85	$111.80
Purchase #7	$233.93	6.637%	$249.4559	$249.46	$249.45	$249.50
7 purchase totals =	$843.27		$909.8805	$909.88	$909.85	$909.80