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	$214.49	4.686%	$224.541	$224.54	$224.55	$224.50
Purchase #2	$222.83	7.854%	$240.3311	$240.33	$240.35	$240.30
Purchase #3	$82.79	7.604%	$89.0854	$89.09	$89.10	$89.10
Purchase #4	$210.42	10.809%	$233.1643	$233.16	$233.15	$233.20
Purchase #5	$102.61	7.218%	$110.0164	$110.02	$110.00	$110.00
Purchase #6	$228.27	13.425%	$258.9152	$258.92	$258.90	$258.90
Purchase #7	$198.32	11.803%	$221.7277	$221.73	$221.75	$221.70
7 purchase totals =	$1,259.73		$1,377.7811	$1,377.79	$1,377.80	$1,377.70