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	$167.45	8.690%	$182.0014	$182.00	$182.00	$182.00
Purchase #2	$83.50	8.850%	$90.8898	$90.89	$90.90	$90.90
Purchase #3	$218.71	12.392%	$245.8125	$245.81	$245.80	$245.80
Purchase #4	$74.98	3.352%	$77.4933	$77.49	$77.50	$77.50
Purchase #5	$194.89	11.799%	$217.8851	$217.89	$217.90	$217.90
Purchase #6	$85.59	8.836%	$93.1527	$93.15	$93.15	$93.20
Purchase #7	$212.86	11.777%	$237.9285	$237.93	$237.95	$237.90
7 purchase totals =	$1,037.98		$1,145.1633	$1,145.16	$1,145.20	$1,145.20