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	$148.75	11.133%	$165.3103	$165.31	$165.30	$165.30
Purchase #2	$171.77	4.430%	$179.3794	$179.38	$179.40	$179.40
Purchase #3	$177.84	10.278%	$196.1184	$196.12	$196.10	$196.10
Purchase #4	$190.73	4.342%	$199.0115	$199.01	$199.00	$199.00
Purchase #5	$41.44	6.792%	$44.2546	$44.25	$44.25	$44.30
Purchase #6	$247.59	6.314%	$263.2228	$263.22	$263.20	$263.20
Purchase #7	$173.66	11.280%	$193.2488	$193.25	$193.25	$193.20
7 purchase totals =	$1,151.78		$1,240.5458	$1,240.54	$1,240.50	$1,240.50