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	$131.93	12.576%	$148.5215	$148.52	$148.50	$148.50
Purchase #2	$33.50	3.200%	$34.572	$34.57	$34.55	$34.60
Purchase #3	$233.47	10.779%	$258.6357	$258.64	$258.65	$258.60
Purchase #4	$230.53	12.417%	$259.1549	$259.15	$259.15	$259.20
Purchase #5	$52.47	3.183%	$54.1401	$54.14	$54.15	$54.10
Purchase #6	$78.96	12.719%	$89.0029	$89.00	$89.00	$89.00
Purchase #7	$117.86	10.751%	$130.5311	$130.53	$130.55	$130.50
7 purchase totals =	$878.72		$974.5582	$974.55	$974.55	$974.50