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	$72.26	9.269%	$78.9578	$78.96	$78.95	$79.00
Purchase #2	$208.95	7.502%	$224.6254	$224.63	$224.65	$224.60
Purchase #3	$25.67	8.707%	$27.9051	$27.91	$27.90	$27.90
Purchase #4	$190.57	5.220%	$200.5178	$200.52	$200.50	$200.50
Purchase #5	$202.35	12.538%	$227.7206	$227.72	$227.70	$227.70
Purchase #6	$197.53	13.702%	$224.5956	$224.60	$224.60	$224.60
Purchase #7	$55.76	12.682%	$62.8315	$62.83	$62.85	$62.80
7 purchase totals =	$953.09		$1,047.1538	$1,047.17	$1,047.15	$1,047.10