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	$129.55	6.418%	$137.8645	$137.86	$137.85	$137.90
Purchase #2	$87.38	4.455%	$91.2728	$91.27	$91.25	$91.30
Purchase #3	$160.34	8.689%	$174.2719	$174.27	$174.25	$174.30
Purchase #4	$207.41	8.186%	$224.3886	$224.39	$224.40	$224.40
Purchase #5	$83.88	10.320%	$92.5364	$92.54	$92.55	$92.50
Purchase #6	$180.95	4.213%	$188.5734	$188.57	$188.55	$188.60
Purchase #7	$166.52	13.755%	$189.4248	$189.42	$189.40	$189.40
7 purchase totals =	$1,016.03		$1,098.3324	$1,098.32	$1,098.25	$1,098.40