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	$85.66	7.300%	$91.9132	$91.91	$91.90	$91.90
Purchase #2	$44.86	6.472%	$47.7633	$47.76	$47.75	$47.80
Purchase #3	$168.45	3.488%	$174.3255	$174.33	$174.35	$174.30
Purchase #4	$250.95	7.195%	$269.0059	$269.01	$269.00	$269.00
Purchase #5	$14.38	3.111%	$14.8274	$14.83	$14.85	$14.80
Purchase #6	$241.95	3.584%	$250.6215	$250.62	$250.60	$250.60
Purchase #7	$83.29	7.655%	$89.6658	$89.67	$89.65	$89.70
7 purchase totals =	$889.54		$938.1226	$938.13	$938.10	$938.10