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	$92.48	5.721%	$97.7708	$97.77	$97.75	$97.80
Purchase #2	$19.63	11.152%	$21.8191	$21.82	$21.80	$21.80
Purchase #3	$121.92	3.443%	$126.1177	$126.12	$126.10	$126.10
Purchase #4	$71.81	9.806%	$78.8517	$78.85	$78.85	$78.90
Purchase #5	$79.59	11.873%	$89.0397	$89.04	$89.05	$89.00
Purchase #6	$71.56	6.603%	$76.2851	$76.29	$76.30	$76.30
Purchase #7	$126.71	3.467%	$131.103	$131.10	$131.10	$131.10
7 purchase totals =	$583.70		$620.9871	$620.99	$620.95	$621.00