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	$58.72	5.731%	$62.0852	$62.09	$62.10	$62.10
Purchase #2	$6.78	13.874%	$7.7207	$7.72	$7.70	$7.70
Purchase #3	$19.31	12.490%	$21.7218	$21.72	$21.70	$21.70
Purchase #4	$184.29	5.753%	$194.8922	$194.89	$194.90	$194.90
Purchase #5	$180.29	3.145%	$185.9601	$185.96	$185.95	$186.00
Purchase #6	$168.61	7.674%	$181.5491	$181.55	$181.55	$181.50
Purchase #7	$45.80	13.682%	$52.0664	$52.07	$52.05	$52.10
7 purchase totals =	$663.80		$705.9955	$706.00	$705.95	$706.00