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	$188.83	4.141%	$196.6495	$196.65	$196.65	$196.60
Purchase #2	$46.94	7.213%	$50.3258	$50.33	$50.35	$50.30
Purchase #3	$123.94	6.599%	$132.1188	$132.12	$132.10	$132.10
Purchase #4	$175.29	5.473%	$184.8836	$184.88	$184.90	$184.90
Purchase #5	$213.76	3.872%	$222.0368	$222.04	$222.05	$222.00
Purchase #6	$188.40	9.773%	$206.8123	$206.81	$206.80	$206.80
Purchase #7	$211.82	7.137%	$226.9376	$226.94	$226.95	$226.90
7 purchase totals =	$1,148.98		$1,219.7644	$1,219.77	$1,219.80	$1,219.60