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	$62.59	5.361%	$65.9454	$65.95	$65.95	$65.90
Purchase #2	$185.84	11.446%	$207.1112	$207.11	$207.10	$207.10
Purchase #3	$124.56	5.357%	$131.2327	$131.23	$131.25	$131.20
Purchase #4	$243.66	7.386%	$261.6567	$261.66	$261.65	$261.70
Purchase #5	$224.69	11.297%	$250.0732	$250.07	$250.05	$250.10
Purchase #6	$231.76	3.694%	$240.3212	$240.32	$240.30	$240.30
Purchase #7	$37.48	8.334%	$40.6036	$40.60	$40.60	$40.60
7 purchase totals =	$1,110.58		$1,196.9440	$1,196.94	$1,196.90	$1,196.90