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	$221.30	12.621%	$249.2303	$249.23	$249.25	$249.20
Purchase #2	$145.27	10.448%	$160.4478	$160.45	$160.45	$160.40
Purchase #3	$192.75	6.424%	$205.1323	$205.13	$205.15	$205.10
Purchase #4	$74.74	3.786%	$77.5697	$77.57	$77.55	$77.60
Purchase #5	$134.43	11.607%	$150.0333	$150.03	$150.05	$150.00
Purchase #6	$37.44	11.216%	$41.6393	$41.64	$41.65	$41.60
Purchase #7	$203.61	11.722%	$227.4772	$227.48	$227.50	$227.50
7 purchase totals =	$1,009.54		$1,111.5299	$1,111.53	$1,111.60	$1,111.40