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	$10.64	7.667%	$11.4558	$11.46	$11.45	$11.50
Purchase #2	$11.82	4.153%	$12.3109	$12.31	$12.30	$12.30
Purchase #3	$226.51	7.859%	$244.3114	$244.31	$244.30	$244.30
Purchase #4	$186.79	3.784%	$193.8581	$193.86	$193.85	$193.90
Purchase #5	$221.39	6.751%	$236.336	$236.34	$236.35	$236.30
Purchase #6	$83.50	8.277%	$90.4113	$90.41	$90.40	$90.40
Purchase #7	$85.33	4.280%	$88.9821	$88.98	$89.00	$89.00
7 purchase totals =	$825.98		$877.6656	$877.67	$877.65	$877.70