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	$152.49	9.688%	$167.2632	$167.26	$167.25	$167.30
Purchase #2	$52.72	8.192%	$57.0388	$57.04	$57.05	$57.00
Purchase #3	$37.56	12.581%	$42.2854	$42.29	$42.30	$42.30
Purchase #4	$123.82	5.312%	$130.3973	$130.40	$130.40	$130.40
Purchase #5	$173.53	8.146%	$187.6658	$187.67	$187.65	$187.70
Purchase #6	$92.76	3.149%	$95.681	$95.68	$95.70	$95.70
Purchase #7	$144.51	13.689%	$164.292	$164.29	$164.30	$164.30
7 purchase totals =	$777.39		$844.6235	$844.63	$844.65	$844.70