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	$118.85	12.850%	$134.1222	$134.12	$134.10	$134.10
Purchase #2	$46.79	7.581%	$50.3371	$50.34	$50.35	$50.30
Purchase #3	$74.74	13.863%	$85.1012	$85.10	$85.10	$85.10
Purchase #4	$196.87	11.407%	$219.327	$219.33	$219.35	$219.30
Purchase #5	$114.42	3.315%	$118.213	$118.21	$118.20	$118.20
Purchase #6	$105.48	5.777%	$111.5736	$111.57	$111.55	$111.60
Purchase #7	$100.85	6.164%	$107.0664	$107.07	$107.05	$107.10
7 purchase totals =	$758.00		$825.7405	$825.74	$825.70	$825.70