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	$250.46	4.255%	$261.1171	$261.12	$261.10	$261.10
Purchase #2	$57.39	3.361%	$59.3189	$59.32	$59.30	$59.30
Purchase #3	$49.68	8.648%	$53.9763	$53.98	$54.00	$54.00
Purchase #4	$76.39	7.526%	$82.1391	$82.14	$82.15	$82.10
Purchase #5	$198.65	8.871%	$216.2722	$216.27	$216.25	$216.30
Purchase #6	$77.54	13.873%	$88.2971	$88.30	$88.30	$88.30
Purchase #7	$145.48	8.730%	$158.1804	$158.18	$158.20	$158.20
7 purchase totals =	$855.59		$919.3011	$919.31	$919.30	$919.30