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	$107.81	5.165%	$113.3784	$113.38	$113.40	$113.40
Purchase #2	$55.75	8.413%	$60.4402	$60.44	$60.45	$60.40
Purchase #3	$160.62	4.796%	$168.3233	$168.32	$168.30	$168.30
Purchase #4	$29.32	11.613%	$32.7249	$32.72	$32.70	$32.70
Purchase #5	$179.63	8.794%	$195.4267	$195.43	$195.45	$195.40
Purchase #6	$30.70	3.857%	$31.8841	$31.88	$31.90	$31.90
Purchase #7	$149.72	9.632%	$164.141	$164.14	$164.15	$164.10
7 purchase totals =	$713.55		$766.3186	$766.31	$766.35	$766.20