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	$168.89	13.366%	$191.4638	$191.46	$191.45	$191.50
Purchase #2	$172.46	10.743%	$190.9874	$190.99	$191.00	$191.00
Purchase #3	$101.58	3.533%	$105.1688	$105.17	$105.15	$105.20
Purchase #4	$101.56	12.516%	$114.2712	$114.27	$114.25	$114.30
Purchase #5	$59.70	12.240%	$67.0073	$67.01	$67.00	$67.00
Purchase #6	$151.33	4.175%	$157.648	$157.65	$157.65	$157.60
Purchase #7	$38.82	6.418%	$41.3115	$41.31	$41.30	$41.30
7 purchase totals =	$794.34		$867.8580	$867.86	$867.80	$867.90