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	$205.63	8.476%	$223.0592	$223.06	$223.05	$223.10
Purchase #2	$158.92	9.241%	$173.6058	$173.61	$173.60	$173.60
Purchase #3	$193.40	10.361%	$213.4382	$213.44	$213.45	$213.40
Purchase #4	$46.47	4.133%	$48.3906	$48.39	$48.40	$48.40
Purchase #5	$36.43	6.747%	$38.8879	$38.89	$38.90	$38.90
Purchase #6	$148.69	11.456%	$165.7239	$165.72	$165.70	$165.70
Purchase #7	$175.76	12.646%	$197.9866	$197.99	$198.00	$198.00
7 purchase totals =	$965.30		$1,061.0922	$1,061.10	$1,061.10	$1,061.10