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	$197.57	11.775%	$220.8339	$220.83	$220.85	$220.80
Purchase #2	$237.71	12.228%	$266.7772	$266.78	$266.80	$266.80
Purchase #3	$66.79	6.305%	$71.0011	$71.00	$71.00	$71.00
Purchase #4	$79.38	3.375%	$82.0591	$82.06	$82.05	$82.10
Purchase #5	$63.86	13.375%	$72.4013	$72.40	$72.40	$72.40
Purchase #6	$195.92	12.479%	$220.3689	$220.37	$220.35	$220.40
Purchase #7	$152.56	9.645%	$167.2744	$167.27	$167.25	$167.30
7 purchase totals =	$993.79		$1,100.7159	$1,100.71	$1,100.70	$1,100.80