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	$73.44	7.250%	$78.7644	$78.76	$78.75	$78.80
Purchase #2	$97.64	7.756%	$105.213	$105.21	$105.20	$105.20
Purchase #3	$61.88	13.718%	$70.3687	$70.37	$70.35	$70.40
Purchase #4	$31.72	5.701%	$33.5284	$33.53	$33.55	$33.50
Purchase #5	$177.93	5.532%	$187.7731	$187.77	$187.75	$187.80
Purchase #6	$242.56	10.335%	$267.6286	$267.63	$267.65	$267.60
Purchase #7	$144.79	6.196%	$153.7612	$153.76	$153.75	$153.80
7 purchase totals =	$829.96		$897.0374	$897.03	$897.00	$897.10