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	$134.50	8.471%	$145.8935	$145.89	$145.90	$145.90
Purchase #2	$115.94	10.281%	$127.8598	$127.86	$127.85	$127.90
Purchase #3	$50.92	13.221%	$57.6521	$57.65	$57.65	$57.70
Purchase #4	$250.29	13.589%	$284.3019	$284.30	$284.30	$284.30
Purchase #5	$206.87	5.837%	$218.945	$218.95	$218.95	$218.90
Purchase #6	$54.49	3.287%	$56.2811	$56.28	$56.30	$56.30
Purchase #7	$246.25	5.311%	$259.3283	$259.33	$259.35	$259.30
7 purchase totals =	$1,059.26		$1,150.2617	$1,150.26	$1,150.30	$1,150.30