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	$218.88	6.693%	$233.5296	$233.53	$233.55	$233.50
Purchase #2	$169.69	7.102%	$181.7414	$181.74	$181.75	$181.70
Purchase #3	$162.41	10.651%	$179.7083	$179.71	$179.70	$179.70
Purchase #4	$19.59	7.389%	$21.0375	$21.04	$21.05	$21.00
Purchase #5	$148.55	9.405%	$162.5211	$162.52	$162.50	$162.50
Purchase #6	$96.25	5.570%	$101.6111	$101.61	$101.60	$101.60
Purchase #7	$211.78	3.756%	$219.7345	$219.73	$219.75	$219.70
7 purchase totals =	$1,027.15		$1,099.8835	$1,099.88	$1,099.90	$1,099.70