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	$247.65	8.287%	$268.1728	$268.17	$268.15	$268.20
Purchase #2	$180.30	8.422%	$195.4849	$195.48	$195.50	$195.50
Purchase #3	$106.70	11.183%	$118.6323	$118.63	$118.65	$118.60
Purchase #4	$146.91	3.484%	$152.0283	$152.03	$152.05	$152.00
Purchase #5	$184.74	7.456%	$198.5142	$198.51	$198.50	$198.50
Purchase #6	$76.69	11.411%	$85.4411	$85.44	$85.45	$85.40
Purchase #7	$144.59	12.225%	$162.2661	$162.27	$162.25	$162.30
7 purchase totals =	$1,087.58		$1,180.5397	$1,180.53	$1,180.55	$1,180.50