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	$246.43	5.340%	$259.5894	$259.59	$259.60	$259.60
Purchase #2	$233.69	7.386%	$250.9503	$250.95	$250.95	$251.00
Purchase #3	$219.41	6.786%	$234.2992	$234.30	$234.30	$234.30
Purchase #4	$49.36	12.350%	$55.456	$55.46	$55.45	$55.50
Purchase #5	$90.82	6.113%	$96.3718	$96.37	$96.35	$96.40
Purchase #6	$94.79	10.284%	$104.5382	$104.54	$104.55	$104.50
Purchase #7	$105.79	5.739%	$111.8613	$111.86	$111.85	$111.90
7 purchase totals =	$1,040.29		$1,113.0662	$1,113.07	$1,113.05	$1,113.20