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	$65.83	11.512%	$73.4083	$73.41	$73.40	$73.40
Purchase #2	$33.70	4.866%	$35.3398	$35.34	$35.35	$35.30
Purchase #3	$196.63	12.767%	$221.7338	$221.73	$221.75	$221.70
Purchase #4	$238.85	10.499%	$263.9269	$263.93	$263.95	$263.90
Purchase #5	$78.89	5.714%	$83.3978	$83.40	$83.40	$83.40
Purchase #6	$97.37	6.489%	$103.6883	$103.69	$103.70	$103.70
Purchase #7	$199.65	13.395%	$226.3931	$226.39	$226.40	$226.40
7 purchase totals =	$910.92		$1,007.8880	$1,007.89	$1,007.95	$1,007.80