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	$126.96	6.427%	$135.1197	$135.12	$135.10	$135.10
Purchase #2	$36.36	4.402%	$37.9606	$37.96	$37.95	$38.00
Purchase #3	$159.59	3.245%	$164.7687	$164.77	$164.75	$164.80
Purchase #4	$104.45	6.766%	$111.5171	$111.52	$111.50	$111.50
Purchase #5	$10.62	3.718%	$11.0149	$11.01	$11.00	$11.00
Purchase #6	$210.92	3.149%	$217.5619	$217.56	$217.55	$217.60
Purchase #7	$74.79	10.277%	$82.4762	$82.48	$82.50	$82.50
7 purchase totals =	$723.69		$760.4191	$760.42	$760.35	$760.50