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	$129.56	12.687%	$145.9973	$146.00	$146.00	$146.00
Purchase #2	$46.71	7.693%	$50.3034	$50.30	$50.30	$50.30
Purchase #3	$249.92	4.470%	$261.0914	$261.09	$261.10	$261.10
Purchase #4	$105.96	12.401%	$119.1001	$119.10	$119.10	$119.10
Purchase #5	$179.45	3.578%	$185.8707	$185.87	$185.85	$185.90
Purchase #6	$86.88	3.488%	$89.9104	$89.91	$89.90	$89.90
Purchase #7	$206.83	8.828%	$225.089	$225.09	$225.10	$225.10
7 purchase totals =	$1,005.31		$1,077.3623	$1,077.36	$1,077.35	$1,077.40