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	$59.39	13.819%	$67.5971	$67.60	$67.60	$67.60
Purchase #2	$88.32	4.118%	$91.957	$91.96	$91.95	$92.00
Purchase #3	$118.70	7.229%	$127.2808	$127.28	$127.30	$127.30
Purchase #4	$125.54	5.812%	$132.8364	$132.84	$132.85	$132.80
Purchase #5	$41.43	8.570%	$44.9806	$44.98	$45.00	$45.00
Purchase #6	$120.84	8.231%	$130.7863	$130.79	$130.80	$130.80
Purchase #7	$123.82	4.659%	$129.5888	$129.59	$129.60	$129.60
7 purchase totals =	$678.04		$725.0270	$725.04	$725.10	$725.10