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	$49.88	4.468%	$52.1086	$52.11	$52.10	$52.10
Purchase #2	$174.90	11.191%	$194.4731	$194.47	$194.45	$194.50
Purchase #3	$196.59	13.299%	$222.7345	$222.73	$222.75	$222.70
Purchase #4	$17.49	8.690%	$19.0099	$19.01	$19.00	$19.00
Purchase #5	$31.55	3.846%	$32.7634	$32.76	$32.75	$32.80
Purchase #6	$103.57	8.641%	$112.5195	$112.52	$112.50	$112.50
Purchase #7	$122.43	11.701%	$136.7555	$136.76	$136.75	$136.80
7 purchase totals =	$696.41		$770.3645	$770.36	$770.30	$770.40