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	$136.29	3.315%	$140.808	$140.81	$140.80	$140.80
Purchase #2	$5.81	8.180%	$6.2853	$6.29	$6.30	$6.30
Purchase #3	$245.54	7.828%	$264.7609	$264.76	$264.75	$264.80
Purchase #4	$157.54	9.674%	$172.7804	$172.78	$172.80	$172.80
Purchase #5	$40.35	6.715%	$43.0595	$43.06	$43.05	$43.10
Purchase #6	$250.36	13.843%	$285.0173	$285.02	$285.00	$285.00
Purchase #7	$99.89	9.792%	$109.6712	$109.67	$109.65	$109.70
7 purchase totals =	$935.78		$1,022.3826	$1,022.39	$1,022.35	$1,022.50