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	$162.71	7.843%	$175.4713	$175.47	$175.45	$175.50
Purchase #2	$121.96	3.777%	$126.5664	$126.57	$126.55	$126.60
Purchase #3	$129.52	12.617%	$145.8615	$145.86	$145.85	$145.90
Purchase #4	$39.42	9.400%	$43.1255	$43.13	$43.15	$43.10
Purchase #5	$167.62	10.419%	$185.0843	$185.08	$185.10	$185.10
Purchase #6	$14.53	11.261%	$16.1662	$16.17	$16.15	$16.20
Purchase #7	$74.42	4.820%	$78.007	$78.01	$78.00	$78.00
7 purchase totals =	$710.18		$770.2822	$770.29	$770.25	$770.40