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	$93.47	3.607%	$96.8415	$96.84	$96.85	$96.80
Purchase #2	$170.27	11.864%	$190.4708	$190.47	$190.45	$190.50
Purchase #3	$113.43	3.482%	$117.3796	$117.38	$117.40	$117.40
Purchase #4	$87.71	11.572%	$97.8598	$97.86	$97.85	$97.90
Purchase #5	$65.83	9.405%	$72.0213	$72.02	$72.00	$72.00
Purchase #6	$189.90	12.216%	$213.0982	$213.10	$213.10	$213.10
Purchase #7	$105.72	3.589%	$109.5143	$109.51	$109.50	$109.50
7 purchase totals =	$826.33		$897.1855	$897.18	$897.15	$897.20