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	$152.58	6.624%	$162.6869	$162.69	$162.70	$162.70
Purchase #2	$145.86	4.372%	$152.237	$152.24	$152.25	$152.20
Purchase #3	$249.40	9.275%	$272.5319	$272.53	$272.55	$272.50
Purchase #4	$94.89	11.721%	$106.0121	$106.01	$106.00	$106.00
Purchase #5	$123.42	11.488%	$137.5985	$137.60	$137.60	$137.60
Purchase #6	$153.94	3.220%	$158.8969	$158.90	$158.90	$158.90
Purchase #7	$109.90	7.477%	$118.1172	$118.12	$118.10	$118.10
7 purchase totals =	$1,029.99		$1,108.0805	$1,108.09	$1,108.10	$1,108.00