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	$108.97	11.303%	$121.2869	$121.29	$121.30	$121.30
Purchase #2	$84.98	9.221%	$92.816	$92.82	$92.80	$92.80
Purchase #3	$65.77	9.347%	$71.9175	$71.92	$71.90	$71.90
Purchase #4	$78.76	9.510%	$86.2501	$86.25	$86.25	$86.30
Purchase #5	$150.55	11.268%	$167.514	$167.51	$167.50	$167.50
Purchase #6	$148.83	11.762%	$166.3354	$166.34	$166.35	$166.30
Purchase #7	$38.58	7.416%	$41.4411	$41.44	$41.45	$41.40
7 purchase totals =	$676.44		$747.5610	$747.57	$747.55	$747.50