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	$80.26	8.790%	$87.3149	$87.31	$87.30	$87.30
Purchase #2	$191.35	7.727%	$206.1356	$206.14	$206.15	$206.10
Purchase #3	$168.33	3.143%	$173.6206	$173.62	$173.60	$173.60
Purchase #4	$39.78	5.220%	$41.8565	$41.86	$41.85	$41.90
Purchase #5	$40.71	4.367%	$42.4878	$42.49	$42.50	$42.50
Purchase #6	$62.43	9.704%	$68.4882	$68.49	$68.50	$68.50
Purchase #7	$124.61	5.709%	$131.724	$131.72	$131.70	$131.70
7 purchase totals =	$707.47		$751.6276	$751.63	$751.60	$751.60