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	$228.33	7.872%	$246.3041	$246.30	$246.30	$246.30
Purchase #2	$233.49	10.775%	$258.6485	$258.65	$258.65	$258.60
Purchase #3	$52.48	3.501%	$54.3173	$54.32	$54.30	$54.30
Purchase #4	$145.26	10.425%	$160.4034	$160.40	$160.40	$160.40
Purchase #5	$206.55	7.685%	$222.4234	$222.42	$222.40	$222.40
Purchase #6	$42.58	3.452%	$44.0499	$44.05	$44.05	$44.00
Purchase #7	$14.68	8.243%	$15.8901	$15.89	$15.90	$15.90
7 purchase totals =	$923.37		$1,002.0367	$1,002.03	$1,002.00	$1,001.90