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	$134.85	13.223%	$152.6812	$152.68	$152.70	$152.70
Purchase #2	$185.50	5.659%	$195.9974	$196.00	$196.00	$196.00
Purchase #3	$191.31	13.111%	$216.3927	$216.39	$216.40	$216.40
Purchase #4	$55.34	7.478%	$59.4783	$59.48	$59.50	$59.50
Purchase #5	$168.55	9.814%	$185.0915	$185.09	$185.10	$185.10
Purchase #6	$180.34	7.562%	$193.9773	$193.98	$194.00	$194.00
Purchase #7	$32.49	5.342%	$34.2256	$34.23	$34.25	$34.20
7 purchase totals =	$948.38		$1,037.8440	$1,037.85	$1,037.95	$1,037.90