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	$82.37	5.507%	$86.9061	$86.91	$86.90	$86.90
Purchase #2	$78.64	5.797%	$83.1988	$83.20	$83.20	$83.20
Purchase #3	$106.85	12.142%	$119.8237	$119.82	$119.80	$119.80
Purchase #4	$39.52	6.683%	$42.1611	$42.16	$42.15	$42.20
Purchase #5	$95.96	12.396%	$107.8552	$107.86	$107.85	$107.90
Purchase #6	$167.65	13.156%	$189.706	$189.71	$189.70	$189.70
Purchase #7	$50.65	4.736%	$53.0488	$53.05	$53.05	$53.00
7 purchase totals =	$621.64		$682.6997	$682.71	$682.65	$682.70