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	$92.82	9.285%	$101.4383	$101.44	$101.45	$101.40
Purchase #2	$60.43	5.251%	$63.6032	$63.60	$63.60	$63.60
Purchase #3	$221.98	12.516%	$249.763	$249.76	$249.75	$249.80
Purchase #4	$54.41	9.192%	$59.4114	$59.41	$59.40	$59.40
Purchase #5	$58.75	13.161%	$66.4821	$66.48	$66.50	$66.50
Purchase #6	$246.62	6.594%	$262.8821	$262.88	$262.90	$262.90
Purchase #7	$222.57	5.380%	$234.5443	$234.54	$234.55	$234.50
7 purchase totals =	$957.58		$1,038.1244	$1,038.11	$1,038.15	$1,038.10