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	$64.64	9.558%	$70.8183	$70.82	$70.80	$70.80
Purchase #2	$29.56	11.656%	$33.0055	$33.01	$33.00	$33.00
Purchase #3	$149.88	9.857%	$164.6537	$164.65	$164.65	$164.70
Purchase #4	$25.78	10.186%	$28.406	$28.41	$28.40	$28.40
Purchase #5	$57.55	12.156%	$64.5458	$64.55	$64.55	$64.50
Purchase #6	$233.49	12.726%	$263.2039	$263.20	$263.20	$263.20
Purchase #7	$53.43	11.717%	$59.6904	$59.69	$59.70	$59.70
7 purchase totals =	$614.33		$684.3236	$684.33	$684.30	$684.30