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	$122.57	7.411%	$131.6537	$131.65	$131.65	$131.70
Purchase #2	$125.62	13.580%	$142.6792	$142.68	$142.70	$142.70
Purchase #3	$101.28	4.450%	$105.787	$105.79	$105.80	$105.80
Purchase #4	$52.70	12.541%	$59.3091	$59.31	$59.30	$59.30
Purchase #5	$197.28	12.687%	$222.3089	$222.31	$222.30	$222.30
Purchase #6	$183.65	9.412%	$200.9351	$200.94	$200.95	$200.90
Purchase #7	$69.43	6.478%	$73.9277	$73.93	$73.95	$73.90
7 purchase totals =	$852.53		$936.6007	$936.61	$936.65	$936.60