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	$192.82	6.565%	$205.4786	$205.48	$205.50	$205.50
Purchase #2	$138.27	3.587%	$143.2297	$143.23	$143.25	$143.20
Purchase #3	$146.76	12.576%	$165.2165	$165.22	$165.20	$165.20
Purchase #4	$153.59	3.599%	$159.1177	$159.12	$159.10	$159.10
Purchase #5	$112.69	9.740%	$123.666	$123.67	$123.65	$123.70
Purchase #6	$102.44	8.799%	$111.4537	$111.45	$111.45	$111.50
Purchase #7	$187.72	6.104%	$199.1784	$199.18	$199.20	$199.20
7 purchase totals =	$1,034.29		$1,107.3406	$1,107.35	$1,107.35	$1,107.40