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	$78.77	10.276%	$86.8644	$86.86	$86.85	$86.90
Purchase #2	$54.30	5.753%	$57.4239	$57.42	$57.40	$57.40
Purchase #3	$90.35	12.578%	$101.7142	$101.71	$101.70	$101.70
Purchase #4	$93.57	12.562%	$105.3243	$105.32	$105.30	$105.30
Purchase #5	$112.56	5.352%	$118.5842	$118.58	$118.60	$118.60
Purchase #6	$123.93	9.168%	$135.2919	$135.29	$135.30	$135.30
Purchase #7	$226.34	5.834%	$239.5447	$239.54	$239.55	$239.50
7 purchase totals =	$779.82		$844.7476	$844.72	$844.70	$844.70