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	$109.61	5.650%	$115.803	$115.80	$115.80	$115.80
Purchase #2	$169.48	12.274%	$190.282	$190.28	$190.30	$190.30
Purchase #3	$245.28	13.722%	$278.9373	$278.94	$278.95	$278.90
Purchase #4	$131.58	8.834%	$143.2038	$143.20	$143.20	$143.20
Purchase #5	$91.89	7.790%	$99.0482	$99.05	$99.05	$99.00
Purchase #6	$51.64	10.146%	$56.8794	$56.88	$56.90	$56.90
Purchase #7	$152.81	4.226%	$159.2678	$159.27	$159.25	$159.30
7 purchase totals =	$952.29		$1,043.4215	$1,043.42	$1,043.45	$1,043.40