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	$75.31	4.673%	$78.8292	$78.83	$78.85	$78.80
Purchase #2	$20.36	7.381%	$21.8628	$21.86	$21.85	$21.90
Purchase #3	$51.29	8.170%	$55.4804	$55.48	$55.50	$55.50
Purchase #4	$20.94	3.282%	$21.6273	$21.63	$21.65	$21.60
Purchase #5	$25.78	9.273%	$28.1706	$28.17	$28.15	$28.20
Purchase #6	$111.81	11.123%	$124.2466	$124.25	$124.25	$124.20
Purchase #7	$178.88	10.302%	$197.3082	$197.31	$197.30	$197.30
7 purchase totals =	$484.37		$527.5251	$527.53	$527.55	$527.50