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	$205.41	11.546%	$229.1266	$229.13	$229.15	$229.10
Purchase #2	$64.67	12.258%	$72.5972	$72.60	$72.60	$72.60
Purchase #3	$249.62	7.296%	$267.8323	$267.83	$267.85	$267.80
Purchase #4	$24.74	13.861%	$28.1692	$28.17	$28.15	$28.20
Purchase #5	$97.52	8.593%	$105.8999	$105.90	$105.90	$105.90
Purchase #6	$91.53	4.817%	$95.939	$95.94	$95.95	$95.90
Purchase #7	$68.97	13.801%	$78.4885	$78.49	$78.50	$78.50
7 purchase totals =	$802.46		$878.0527	$878.06	$878.10	$878.00