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	$176.87	3.687%	$183.3912	$183.39	$183.40	$183.40
Purchase #2	$44.72	8.588%	$48.5606	$48.56	$48.55	$48.60
Purchase #3	$165.88	8.196%	$179.4755	$179.48	$179.50	$179.50
Purchase #4	$34.99	12.789%	$39.4649	$39.46	$39.45	$39.50
Purchase #5	$218.31	11.654%	$243.7518	$243.75	$243.75	$243.80
Purchase #6	$65.41	10.304%	$72.1498	$72.15	$72.15	$72.10
Purchase #7	$17.89	7.852%	$19.2947	$19.29	$19.30	$19.30
7 purchase totals =	$724.07		$786.0885	$786.08	$786.10	$786.20