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	$65.47	12.490%	$73.6472	$73.65	$73.65	$73.60
Purchase #2	$156.60	3.753%	$162.4772	$162.48	$162.50	$162.50
Purchase #3	$98.46	12.299%	$110.5696	$110.57	$110.55	$110.60
Purchase #4	$10.52	9.394%	$11.5082	$11.51	$11.50	$11.50
Purchase #5	$50.82	8.728%	$55.2556	$55.26	$55.25	$55.30
Purchase #6	$44.47	4.764%	$46.5886	$46.59	$46.60	$46.60
Purchase #7	$98.55	11.142%	$109.5304	$109.53	$109.55	$109.50
7 purchase totals =	$524.89		$569.5768	$569.59	$569.60	$569.60