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	$42.59	3.232%	$43.9665	$43.97	$43.95	$44.00
Purchase #2	$236.90	11.577%	$264.3259	$264.33	$264.35	$264.30
Purchase #3	$227.46	10.121%	$250.4812	$250.48	$250.50	$250.50
Purchase #4	$151.60	11.494%	$169.0249	$169.02	$169.00	$169.00
Purchase #5	$107.25	11.515%	$119.5998	$119.60	$119.60	$119.60
Purchase #6	$58.74	4.388%	$61.3175	$61.32	$61.30	$61.30
Purchase #7	$58.29	5.507%	$61.5	$61.50	$61.50	$61.50
7 purchase totals =	$882.83		$970.2158	$970.22	$970.20	$970.20