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	$52.68	4.381%	$54.9879	$54.99	$55.00	$55.00
Purchase #2	$64.44	10.201%	$71.0135	$71.01	$71.00	$71.00
Purchase #3	$229.46	6.707%	$244.8499	$244.85	$244.85	$244.80
Purchase #4	$122.33	7.337%	$131.3054	$131.31	$131.30	$131.30
Purchase #5	$52.80	5.690%	$55.8043	$55.80	$55.80	$55.80
Purchase #6	$80.74	7.186%	$86.542	$86.54	$86.55	$86.50
Purchase #7	$73.42	6.242%	$78.0029	$78.00	$78.00	$78.00
7 purchase totals =	$675.87		$722.5059	$722.50	$722.50	$722.40