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	$66.64	3.302%	$68.8405	$68.84	$68.85	$68.80
Purchase #2	$147.45	10.410%	$162.7995	$162.80	$162.80	$162.80
Purchase #3	$173.40	4.545%	$181.281	$181.28	$181.30	$181.30
Purchase #4	$141.33	10.742%	$156.5117	$156.51	$156.50	$156.50
Purchase #5	$180.44	5.270%	$189.9492	$189.95	$189.95	$189.90
Purchase #6	$52.50	4.315%	$54.7654	$54.77	$54.75	$54.80
Purchase #7	$39.43	11.390%	$43.9211	$43.92	$43.90	$43.90
7 purchase totals =	$801.19		$858.0684	$858.07	$858.05	$858.00