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	$195.91	13.732%	$222.8124	$222.81	$222.80	$222.80
Purchase #2	$245.36	12.549%	$276.1502	$276.15	$276.15	$276.20
Purchase #3	$116.92	11.851%	$130.7762	$130.78	$130.80	$130.80
Purchase #4	$55.45	3.228%	$57.2399	$57.24	$57.25	$57.20
Purchase #5	$71.78	9.376%	$78.5101	$78.51	$78.50	$78.50
Purchase #6	$149.71	9.792%	$164.3696	$164.37	$164.35	$164.40
Purchase #7	$109.64	6.869%	$117.1712	$117.17	$117.15	$117.20
7 purchase totals =	$944.77		$1,047.0296	$1,047.03	$1,047.00	$1,047.10