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	$125.46	12.871%	$141.608	$141.61	$141.60	$141.60
Purchase #2	$97.71	10.223%	$107.6989	$107.70	$107.70	$107.70
Purchase #3	$134.97	12.742%	$152.1679	$152.17	$152.15	$152.20
Purchase #4	$184.89	13.663%	$210.1515	$210.15	$210.15	$210.20
Purchase #5	$70.59	11.294%	$78.5624	$78.56	$78.55	$78.60
Purchase #6	$78.98	10.486%	$87.2618	$87.26	$87.25	$87.30
Purchase #7	$64.89	4.503%	$67.812	$67.81	$67.80	$67.80
7 purchase totals =	$757.49		$845.2625	$845.26	$845.20	$845.40