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	$79.51	13.623%	$90.3416	$90.34	$90.35	$90.30
Purchase #2	$128.65	11.691%	$143.6905	$143.69	$143.70	$143.70
Purchase #3	$128.25	11.750%	$143.3194	$143.32	$143.30	$143.30
Purchase #4	$117.62	7.150%	$126.0298	$126.03	$126.05	$126.00
Purchase #5	$164.26	8.690%	$178.5342	$178.53	$178.55	$178.50
Purchase #6	$140.95	4.706%	$147.5831	$147.58	$147.60	$147.60
Purchase #7	$171.41	5.496%	$180.8307	$180.83	$180.85	$180.80
7 purchase totals =	$930.65		$1,010.3293	$1,010.32	$1,010.40	$1,010.20