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	$103.31	7.645%	$111.208	$111.21	$111.20	$111.20
Purchase #2	$181.83	7.277%	$195.0618	$195.06	$195.05	$195.10
Purchase #3	$67.55	13.360%	$76.5747	$76.57	$76.55	$76.60
Purchase #4	$61.67	13.379%	$69.9208	$69.92	$69.90	$69.90
Purchase #5	$133.49	5.397%	$140.6945	$140.69	$140.70	$140.70
Purchase #6	$40.97	10.839%	$45.4107	$45.41	$45.40	$45.40
Purchase #7	$85.64	6.274%	$91.0131	$91.01	$91.00	$91.00
7 purchase totals =	$674.46		$729.8836	$729.87	$729.80	$729.90