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	$153.75	5.433%	$162.1032	$162.10	$162.10	$162.10
Purchase #2	$227.90	10.124%	$250.9726	$250.97	$250.95	$251.00
Purchase #3	$127.38	13.696%	$144.826	$144.83	$144.85	$144.80
Purchase #4	$239.57	4.826%	$251.1316	$251.13	$251.15	$251.10
Purchase #5	$105.62	5.293%	$111.2105	$111.21	$111.20	$111.20
Purchase #6	$150.61	5.535%	$158.9463	$158.95	$158.95	$158.90
Purchase #7	$171.89	9.377%	$188.0081	$188.01	$188.00	$188.00
7 purchase totals =	$1,176.72		$1,267.1983	$1,267.20	$1,267.20	$1,267.10