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	$74.77	5.510%	$78.8898	$78.89	$78.90	$78.90
Purchase #2	$91.34	9.265%	$99.8027	$99.80	$99.80	$99.80
Purchase #3	$225.74	4.701%	$236.352	$236.35	$236.35	$236.40
Purchase #4	$226.29	8.317%	$245.1105	$245.11	$245.10	$245.10
Purchase #5	$83.72	13.512%	$95.0322	$95.03	$95.05	$95.00
Purchase #6	$132.84	8.599%	$144.2629	$144.26	$144.25	$144.30
Purchase #7	$233.77	13.567%	$265.4856	$265.49	$265.50	$265.50
7 purchase totals =	$1,068.47		$1,164.9357	$1,164.93	$1,164.95	$1,165.00