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	$209.84	11.427%	$233.8184	$233.82	$233.80	$233.80
Purchase #2	$143.98	12.856%	$162.4901	$162.49	$162.50	$162.50
Purchase #3	$238.86	10.579%	$264.129	$264.13	$264.15	$264.10
Purchase #4	$13.96	5.790%	$14.7683	$14.77	$14.75	$14.80
Purchase #5	$161.38	9.399%	$176.5481	$176.55	$176.55	$176.50
Purchase #6	$62.98	5.515%	$66.4533	$66.45	$66.45	$66.50
Purchase #7	$104.39	6.355%	$111.024	$111.02	$111.00	$111.00
7 purchase totals =	$935.39		$1,029.2312	$1,029.23	$1,029.20	$1,029.20