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	$136.76	3.571%	$141.6437	$141.64	$141.65	$141.60
Purchase #2	$97.97	5.194%	$103.0586	$103.06	$103.05	$103.10
Purchase #3	$84.77	5.302%	$89.2645	$89.26	$89.25	$89.30
Purchase #4	$65.37	11.849%	$73.1157	$73.12	$73.10	$73.10
Purchase #5	$173.87	3.261%	$179.5399	$179.54	$179.55	$179.50
Purchase #6	$43.61	6.641%	$46.5061	$46.51	$46.50	$46.50
Purchase #7	$80.91	3.480%	$83.7257	$83.73	$83.75	$83.70
7 purchase totals =	$683.26		$716.8542	$716.86	$716.85	$716.80