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	$120.64	11.466%	$134.4726	$134.47	$134.45	$134.50
Purchase #2	$171.54	9.367%	$187.6082	$187.61	$187.60	$187.60
Purchase #3	$215.74	10.281%	$237.9202	$237.92	$237.90	$237.90
Purchase #4	$89.84	11.385%	$100.0683	$100.07	$100.05	$100.10
Purchase #5	$228.36	4.124%	$237.7776	$237.78	$237.80	$237.80
Purchase #6	$156.49	3.583%	$162.097	$162.10	$162.10	$162.10
Purchase #7	$145.25	3.634%	$150.5284	$150.53	$150.55	$150.50
7 purchase totals =	$1,127.86		$1,210.4723	$1,210.48	$1,210.45	$1,210.50