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	$42.65	5.651%	$45.0602	$45.06	$45.05	$45.10
Purchase #2	$142.90	9.437%	$156.3855	$156.39	$156.40	$156.40
Purchase #3	$205.51	10.634%	$227.3639	$227.36	$227.35	$227.40
Purchase #4	$204.97	12.755%	$231.1139	$231.11	$231.10	$231.10
Purchase #5	$190.37	4.741%	$199.3954	$199.40	$199.40	$199.40
Purchase #6	$93.25	7.264%	$100.0237	$100.02	$100.00	$100.00
Purchase #7	$53.47	8.726%	$58.1358	$58.14	$58.15	$58.10
7 purchase totals =	$933.12		$1,017.4784	$1,017.48	$1,017.45	$1,017.50