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	$156.64	12.497%	$176.2153	$176.22	$176.20	$176.20
Purchase #2	$98.61	4.712%	$103.2565	$103.26	$103.25	$103.30
Purchase #3	$238.28	12.170%	$267.2787	$267.28	$267.30	$267.30
Purchase #4	$158.40	7.459%	$170.2151	$170.22	$170.20	$170.20
Purchase #5	$168.50	3.647%	$174.6452	$174.65	$174.65	$174.60
Purchase #6	$92.40	13.520%	$104.8925	$104.89	$104.90	$104.90
Purchase #7	$42.83	13.335%	$48.5414	$48.54	$48.55	$48.50
7 purchase totals =	$955.66		$1,045.0447	$1,045.06	$1,045.05	$1,045.00