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	$163.60	5.356%	$172.3624	$172.36	$172.35	$172.40
Purchase #2	$67.83	4.108%	$70.6165	$70.62	$70.60	$70.60
Purchase #3	$27.84	6.728%	$29.7131	$29.71	$29.70	$29.70
Purchase #4	$137.25	11.158%	$152.5644	$152.56	$152.55	$152.60
Purchase #5	$245.31	4.687%	$256.8077	$256.81	$256.80	$256.80
Purchase #6	$72.35	8.631%	$78.5945	$78.59	$78.60	$78.60
Purchase #7	$57.51	13.501%	$65.2744	$65.27	$65.25	$65.30
7 purchase totals =	$771.69		$825.9330	$825.92	$825.85	$826.00