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	$186.40	5.487%	$196.6278	$196.63	$196.65	$196.60
Purchase #2	$218.35	7.178%	$234.0232	$234.02	$234.00	$234.00
Purchase #3	$157.84	5.689%	$166.8195	$166.82	$166.80	$166.80
Purchase #4	$76.59	11.398%	$85.3197	$85.32	$85.30	$85.30
Purchase #5	$118.87	7.753%	$128.086	$128.09	$128.10	$128.10
Purchase #6	$214.84	11.748%	$240.0794	$240.08	$240.10	$240.10
Purchase #7	$50.44	10.376%	$55.6737	$55.67	$55.65	$55.70
7 purchase totals =	$1,023.33		$1,106.6293	$1,106.63	$1,106.60	$1,106.60