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	$196.27	13.345%	$222.4622	$222.46	$222.45	$222.50
Purchase #2	$87.34	6.473%	$92.9935	$92.99	$93.00	$93.00
Purchase #3	$45.54	11.268%	$50.6714	$50.67	$50.65	$50.70
Purchase #4	$97.89	6.145%	$103.9053	$103.91	$103.90	$103.90
Purchase #5	$199.26	10.566%	$220.3138	$220.31	$220.30	$220.30
Purchase #6	$10.91	10.841%	$12.0928	$12.09	$12.10	$12.10
Purchase #7	$232.30	3.140%	$239.5942	$239.59	$239.60	$239.60
7 purchase totals =	$869.51		$942.0332	$942.02	$942.00	$942.10