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	$183.66	3.858%	$190.7456	$190.75	$190.75	$190.70
Purchase #2	$202.52	9.757%	$222.2799	$222.28	$222.30	$222.30
Purchase #3	$44.62	5.109%	$46.8996	$46.90	$46.90	$46.90
Purchase #4	$116.36	9.394%	$127.2909	$127.29	$127.30	$127.30
Purchase #5	$150.37	13.653%	$170.9	$170.90	$170.90	$170.90
Purchase #6	$217.47	10.499%	$240.3022	$240.30	$240.30	$240.30
Purchase #7	$22.39	4.737%	$23.4506	$23.45	$23.45	$23.50
7 purchase totals =	$937.39		$1,021.8688	$1,021.87	$1,021.90	$1,021.90