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	$70.60	11.856%	$78.9703	$78.97	$78.95	$79.00
Purchase #2	$144.91	10.444%	$160.0444	$160.04	$160.05	$160.00
Purchase #3	$50.58	11.319%	$56.3052	$56.31	$56.30	$56.30
Purchase #4	$127.33	12.733%	$143.5429	$143.54	$143.55	$143.50
Purchase #5	$154.50	10.400%	$170.568	$170.57	$170.55	$170.60
Purchase #6	$204.97	6.345%	$217.9753	$217.98	$218.00	$218.00
Purchase #7	$221.83	5.349%	$233.6957	$233.70	$233.70	$233.70
7 purchase totals =	$974.72		$1,061.1018	$1,061.11	$1,061.10	$1,061.10