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	$218.28	10.275%	$240.7083	$240.71	$240.70	$240.70
Purchase #2	$167.51	13.153%	$189.5426	$189.54	$189.55	$189.50
Purchase #3	$85.87	8.282%	$92.9818	$92.98	$93.00	$93.00
Purchase #4	$192.92	11.328%	$214.774	$214.77	$214.75	$214.80
Purchase #5	$75.30	13.839%	$85.7208	$85.72	$85.70	$85.70
Purchase #6	$230.72	4.580%	$241.287	$241.29	$241.30	$241.30
Purchase #7	$200.41	11.413%	$223.2828	$223.28	$223.30	$223.30
7 purchase totals =	$1,171.01		$1,288.2973	$1,288.29	$1,288.30	$1,288.30