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	$149.29	10.158%	$164.4549	$164.45	$164.45	$164.50
Purchase #2	$44.78	11.736%	$50.0354	$50.04	$50.05	$50.00
Purchase #3	$53.96	6.796%	$57.6271	$57.63	$57.65	$57.60
Purchase #4	$247.51	7.582%	$266.2762	$266.28	$266.30	$266.30
Purchase #5	$9.49	13.824%	$10.8019	$10.80	$10.80	$10.80
Purchase #6	$40.76	3.112%	$42.0285	$42.03	$42.05	$42.00
Purchase #7	$210.27	6.293%	$223.5023	$223.50	$223.50	$223.50
7 purchase totals =	$756.06		$814.7263	$814.73	$814.80	$814.70