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	$156.54	6.729%	$167.0736	$167.07	$167.05	$167.10
Purchase #2	$55.98	6.527%	$59.6338	$59.63	$59.65	$59.60
Purchase #3	$204.96	12.640%	$230.8669	$230.87	$230.85	$230.90
Purchase #4	$192.55	9.311%	$210.4783	$210.48	$210.50	$210.50
Purchase #5	$6.32	4.637%	$6.6131	$6.61	$6.60	$6.60
Purchase #6	$167.54	12.435%	$188.3736	$188.37	$188.35	$188.40
Purchase #7	$174.93	7.707%	$188.4119	$188.41	$188.40	$188.40
7 purchase totals =	$958.82		$1,051.4512	$1,051.44	$1,051.40	$1,051.50