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	$250.44	12.830%	$282.5715	$282.57	$282.55	$282.60
Purchase #2	$247.39	8.646%	$268.7793	$268.78	$268.80	$268.80
Purchase #3	$87.48	10.751%	$96.885	$96.89	$96.90	$96.90
Purchase #4	$216.72	10.147%	$238.7106	$238.71	$238.70	$238.70
Purchase #5	$53.87	10.586%	$59.5727	$59.57	$59.55	$59.60
Purchase #6	$95.95	6.449%	$102.1378	$102.14	$102.15	$102.10
Purchase #7	$46.87	11.579%	$52.2971	$52.30	$52.30	$52.30
7 purchase totals =	$998.72		$1,100.9540	$1,100.96	$1,100.95	$1,101.00