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	$71.59	3.154%	$73.8479	$73.85	$73.85	$73.80
Purchase #2	$43.95	3.571%	$45.5195	$45.52	$45.50	$45.50
Purchase #3	$189.45	3.305%	$195.7113	$195.71	$195.70	$195.70
Purchase #4	$198.74	6.102%	$210.8671	$210.87	$210.85	$210.90
Purchase #5	$60.52	11.314%	$67.3672	$67.37	$67.35	$67.40
Purchase #6	$170.90	5.150%	$179.7014	$179.70	$179.70	$179.70
Purchase #7	$152.93	12.859%	$172.5953	$172.60	$172.60	$172.60
7 purchase totals =	$888.08		$945.6097	$945.62	$945.55	$945.60