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	$178.99	13.731%	$203.5671	$203.57	$203.55	$203.60
Purchase #2	$104.32	4.651%	$109.1719	$109.17	$109.15	$109.20
Purchase #3	$212.98	9.653%	$233.539	$233.54	$233.55	$233.50
Purchase #4	$75.57	8.715%	$82.1559	$82.16	$82.15	$82.20
Purchase #5	$36.57	4.662%	$38.2749	$38.27	$38.25	$38.30
Purchase #6	$190.66	7.567%	$205.0872	$205.09	$205.10	$205.10
Purchase #7	$211.56	10.592%	$233.9684	$233.97	$233.95	$234.00
7 purchase totals =	$1,010.65		$1,105.7644	$1,105.77	$1,105.70	$1,105.90