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	$250.72	4.526%	$262.0676	$262.07	$262.05	$262.10
Purchase #2	$44.81	4.600%	$46.8713	$46.87	$46.85	$46.90
Purchase #3	$18.50	4.737%	$19.3763	$19.38	$19.40	$19.40
Purchase #4	$93.69	12.528%	$105.4275	$105.43	$105.45	$105.40
Purchase #5	$114.89	11.504%	$128.1069	$128.11	$128.10	$128.10
Purchase #6	$79.99	12.203%	$89.7512	$89.75	$89.75	$89.80
Purchase #7	$35.27	7.394%	$37.8779	$37.88	$37.90	$37.90
7 purchase totals =	$637.87		$689.4787	$689.49	$689.50	$689.60