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	$200.79	10.834%	$222.5436	$222.54	$222.55	$222.50
Purchase #2	$113.55	13.621%	$129.0166	$129.02	$129.00	$129.00
Purchase #3	$32.70	3.461%	$33.8317	$33.83	$33.85	$33.80
Purchase #4	$105.57	13.632%	$119.9613	$119.96	$119.95	$120.00
Purchase #5	$225.45	7.483%	$242.3204	$242.32	$242.30	$242.30
Purchase #6	$201.47	7.852%	$217.2894	$217.29	$217.30	$217.30
Purchase #7	$74.27	8.589%	$80.6491	$80.65	$80.65	$80.60
7 purchase totals =	$953.80		$1,045.6121	$1,045.61	$1,045.60	$1,045.50