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	$189.84	3.358%	$196.2148	$196.21	$196.20	$196.20
Purchase #2	$152.45	12.450%	$171.43	$171.43	$171.45	$171.40
Purchase #3	$42.72	13.732%	$48.5863	$48.59	$48.60	$48.60
Purchase #4	$10.88	5.576%	$11.4867	$11.49	$11.50	$11.50
Purchase #5	$125.41	3.225%	$129.4545	$129.45	$129.45	$129.50
Purchase #6	$186.67	10.105%	$205.533	$205.53	$205.55	$205.50
Purchase #7	$245.94	7.727%	$264.9438	$264.94	$264.95	$264.90
7 purchase totals =	$953.91		$1,027.6491	$1,027.64	$1,027.70	$1,027.60