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	$96.47	4.515%	$100.8256	$100.83	$100.85	$100.80
Purchase #2	$13.99	5.393%	$14.7445	$14.74	$14.75	$14.70
Purchase #3	$71.28	10.622%	$78.8514	$78.85	$78.85	$78.90
Purchase #4	$229.61	10.633%	$254.0244	$254.02	$254.00	$254.00
Purchase #5	$214.30	11.874%	$239.746	$239.75	$239.75	$239.70
Purchase #6	$230.51	4.366%	$240.5741	$240.57	$240.55	$240.60
Purchase #7	$124.74	10.406%	$137.7204	$137.72	$137.70	$137.70
7 purchase totals =	$980.90		$1,066.4864	$1,066.48	$1,066.45	$1,066.40