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	$217.48	5.586%	$229.6284	$229.63	$229.65	$229.60
Purchase #2	$74.71	8.223%	$80.8534	$80.85	$80.85	$80.90
Purchase #3	$186.65	4.476%	$195.0045	$195.00	$195.00	$195.00
Purchase #4	$120.86	8.659%	$131.3253	$131.33	$131.35	$131.30
Purchase #5	$159.27	5.766%	$168.4535	$168.45	$168.45	$168.50
Purchase #6	$93.41	6.592%	$99.5676	$99.57	$99.55	$99.60
Purchase #7	$159.82	13.411%	$181.2535	$181.25	$181.25	$181.30
7 purchase totals =	$1,012.20		$1,086.0862	$1,086.08	$1,086.10	$1,086.20