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	$134.48	4.614%	$140.6849	$140.68	$140.70	$140.70
Purchase #2	$26.70	5.350%	$28.1285	$28.13	$28.15	$28.10
Purchase #3	$19.35	6.329%	$20.5747	$20.57	$20.55	$20.60
Purchase #4	$70.25	11.172%	$78.0983	$78.10	$78.10	$78.10
Purchase #5	$82.73	13.198%	$93.6487	$93.65	$93.65	$93.60
Purchase #6	$48.67	11.786%	$54.4062	$54.41	$54.40	$54.40
Purchase #7	$233.42	7.721%	$251.4424	$251.44	$251.45	$251.40
7 purchase totals =	$615.60		$666.9837	$666.98	$667.00	$666.90