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	$197.33	11.256%	$219.5415	$219.54	$219.55	$219.50
Purchase #2	$44.52	11.317%	$49.5583	$49.56	$49.55	$49.60
Purchase #3	$46.49	12.206%	$52.1646	$52.16	$52.15	$52.20
Purchase #4	$128.46	12.225%	$144.1642	$144.16	$144.15	$144.20
Purchase #5	$153.96	4.138%	$160.3309	$160.33	$160.35	$160.30
Purchase #6	$12.64	6.217%	$13.4258	$13.43	$13.45	$13.40
Purchase #7	$80.57	12.143%	$90.3536	$90.35	$90.35	$90.40
7 purchase totals =	$663.97		$729.5389	$729.53	$729.55	$729.60