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	$208.50	11.122%	$231.6894	$231.69	$231.70	$231.70
Purchase #2	$237.47	8.146%	$256.8143	$256.81	$256.80	$256.80
Purchase #3	$134.29	4.414%	$140.2176	$140.22	$140.20	$140.20
Purchase #4	$133.94	12.528%	$150.72	$150.72	$150.70	$150.70
Purchase #5	$211.27	8.385%	$228.985	$228.99	$229.00	$229.00
Purchase #6	$102.85	6.481%	$109.5157	$109.52	$109.50	$109.50
Purchase #7	$65.42	12.522%	$73.6119	$73.61	$73.60	$73.60
7 purchase totals =	$1,093.74		$1,191.5539	$1,191.56	$1,191.50	$1,191.50