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	$215.52	6.341%	$229.1861	$229.19	$229.20	$229.20
Purchase #2	$205.45	6.762%	$219.3425	$219.34	$219.35	$219.30
Purchase #3	$33.80	9.482%	$37.0049	$37.00	$37.00	$37.00
Purchase #4	$137.71	4.599%	$144.0433	$144.04	$144.05	$144.00
Purchase #5	$237.39	6.721%	$253.345	$253.35	$253.35	$253.30
Purchase #6	$144.81	4.198%	$150.8891	$150.89	$150.90	$150.90
Purchase #7	$105.27	3.859%	$109.3324	$109.33	$109.35	$109.30
7 purchase totals =	$1,079.95		$1,143.1433	$1,143.14	$1,143.20	$1,143.00