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	$94.83	5.626%	$100.1651	$100.17	$100.15	$100.20
Purchase #2	$211.82	8.659%	$230.1615	$230.16	$230.15	$230.20
Purchase #3	$90.67	5.229%	$95.4111	$95.41	$95.40	$95.40
Purchase #4	$190.79	10.377%	$210.5883	$210.59	$210.60	$210.60
Purchase #5	$101.72	10.573%	$112.4749	$112.47	$112.45	$112.50
Purchase #6	$246.53	7.270%	$264.4527	$264.45	$264.45	$264.50
Purchase #7	$120.91	6.712%	$129.0255	$129.03	$129.05	$129.00
7 purchase totals =	$1,057.27		$1,142.2791	$1,142.28	$1,142.25	$1,142.40