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	$114.68	13.695%	$130.3854	$130.39	$130.40	$130.40
Purchase #2	$35.63	12.711%	$40.1589	$40.16	$40.15	$40.20
Purchase #3	$52.54	3.730%	$54.4997	$54.50	$54.50	$54.50
Purchase #4	$104.42	5.354%	$110.0106	$110.01	$110.00	$110.00
Purchase #5	$191.81	4.613%	$200.6582	$200.66	$200.65	$200.70
Purchase #6	$210.47	12.756%	$237.3176	$237.32	$237.30	$237.30
Purchase #7	$70.50	3.335%	$72.8512	$72.85	$72.85	$72.90
7 purchase totals =	$780.05		$845.8816	$845.89	$845.85	$846.00