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	$192.44	3.437%	$199.0542	$199.05	$199.05	$199.10
Purchase #2	$158.94	10.559%	$175.7225	$175.72	$175.70	$175.70
Purchase #3	$127.41	10.707%	$141.0518	$141.05	$141.05	$141.10
Purchase #4	$153.26	10.135%	$168.7929	$168.79	$168.80	$168.80
Purchase #5	$158.37	8.556%	$171.9201	$171.92	$171.90	$171.90
Purchase #6	$196.88	13.404%	$223.2698	$223.27	$223.25	$223.30
Purchase #7	$15.65	3.795%	$16.2439	$16.24	$16.25	$16.20
7 purchase totals =	$1,002.95		$1,096.0552	$1,096.04	$1,096.00	$1,096.10