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	$240.29	11.758%	$268.5433	$268.54	$268.55	$268.50
Purchase #2	$20.73	3.638%	$21.4842	$21.48	$21.50	$21.50
Purchase #3	$56.96	4.234%	$59.3717	$59.37	$59.35	$59.40
Purchase #4	$151.81	11.201%	$168.8142	$168.81	$168.80	$168.80
Purchase #5	$203.34	6.609%	$216.7787	$216.78	$216.80	$216.80
Purchase #6	$66.35	7.531%	$71.3468	$71.35	$71.35	$71.30
Purchase #7	$234.42	5.520%	$247.36	$247.36	$247.35	$247.40
7 purchase totals =	$973.90		$1,053.6989	$1,053.69	$1,053.70	$1,053.70