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	$48.72	7.537%	$52.392	$52.39	$52.40	$52.40
Purchase #2	$186.66	11.487%	$208.1016	$208.10	$208.10	$208.10
Purchase #3	$158.83	9.695%	$174.2286	$174.23	$174.25	$174.20
Purchase #4	$46.62	13.248%	$52.7962	$52.80	$52.80	$52.80
Purchase #5	$156.53	5.502%	$165.1423	$165.14	$165.15	$165.10
Purchase #6	$215.82	11.288%	$240.1818	$240.18	$240.20	$240.20
Purchase #7	$183.76	13.201%	$208.0182	$208.02	$208.00	$208.00
7 purchase totals =	$996.94		$1,100.8607	$1,100.86	$1,100.90	$1,100.80