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	$208.54	3.294%	$215.4093	$215.41	$215.40	$215.40
Purchase #2	$128.30	13.235%	$145.2805	$145.28	$145.30	$145.30
Purchase #3	$97.30	11.534%	$108.5226	$108.52	$108.50	$108.50
Purchase #4	$208.57	9.464%	$228.3091	$228.31	$228.30	$228.30
Purchase #5	$105.33	7.373%	$113.096	$113.10	$113.10	$113.10
Purchase #6	$88.46	13.195%	$100.1323	$100.13	$100.15	$100.10
Purchase #7	$86.99	5.636%	$91.8928	$91.89	$91.90	$91.90
7 purchase totals =	$923.49		$1,002.6426	$1,002.64	$1,002.65	$1,002.60