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	$179.63	11.523%	$200.3288	$200.33	$200.35	$200.30
Purchase #2	$85.34	5.227%	$89.8007	$89.80	$89.80	$89.80
Purchase #3	$237.58	10.507%	$262.5425	$262.54	$262.55	$262.50
Purchase #4	$123.56	13.289%	$139.9799	$139.98	$140.00	$140.00
Purchase #5	$240.71	9.167%	$262.7759	$262.78	$262.80	$262.80
Purchase #6	$162.92	12.371%	$183.0748	$183.07	$183.05	$183.10
Purchase #7	$215.57	8.132%	$233.1002	$233.10	$233.10	$233.10
7 purchase totals =	$1,245.31		$1,371.6028	$1,371.60	$1,371.65	$1,371.60