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	$191.34	10.218%	$210.8911	$210.89	$210.90	$210.90
Purchase #2	$76.35	6.113%	$81.0173	$81.02	$81.00	$81.00
Purchase #3	$41.47	5.118%	$43.5924	$43.59	$43.60	$43.60
Purchase #4	$91.87	9.227%	$100.3468	$100.35	$100.35	$100.30
Purchase #5	$216.37	3.517%	$223.9797	$223.98	$224.00	$224.00
Purchase #6	$38.25	12.743%	$43.1242	$43.12	$43.10	$43.10
Purchase #7	$127.94	4.383%	$133.5476	$133.55	$133.55	$133.50
7 purchase totals =	$783.59		$836.4991	$836.50	$836.50	$836.40