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	$222.52	10.670%	$246.2629	$246.26	$246.25	$246.30
Purchase #2	$147.68	8.785%	$160.6537	$160.65	$160.65	$160.70
Purchase #3	$179.57	6.387%	$191.0391	$191.04	$191.05	$191.00
Purchase #4	$54.63	8.512%	$59.2801	$59.28	$59.30	$59.30
Purchase #5	$75.70	9.393%	$82.8105	$82.81	$82.80	$82.80
Purchase #6	$29.68	9.499%	$32.4993	$32.50	$32.50	$32.50
Purchase #7	$231.26	5.220%	$243.3318	$243.33	$243.35	$243.30
7 purchase totals =	$941.04		$1,015.8774	$1,015.87	$1,015.90	$1,015.90