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	$30.95	4.698%	$32.404	$32.40	$32.40	$32.40
Purchase #2	$40.48	13.761%	$46.0505	$46.05	$46.05	$46.10
Purchase #3	$37.91	4.524%	$39.625	$39.63	$39.65	$39.60
Purchase #4	$239.38	11.700%	$267.3875	$267.39	$267.40	$267.40
Purchase #5	$177.64	8.578%	$192.878	$192.88	$192.90	$192.90
Purchase #6	$37.34	13.454%	$42.3637	$42.36	$42.35	$42.40
Purchase #7	$164.76	13.730%	$187.3815	$187.38	$187.40	$187.40
7 purchase totals =	$728.46		$808.0902	$808.09	$808.15	$808.20