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	$103.69	5.675%	$109.5744	$109.57	$109.55	$109.60
Purchase #2	$200.87	11.324%	$223.6165	$223.62	$223.60	$223.60
Purchase #3	$39.62	3.184%	$40.8815	$40.88	$40.90	$40.90
Purchase #4	$23.45	3.113%	$24.18	$24.18	$24.20	$24.20
Purchase #5	$68.34	6.683%	$72.9072	$72.91	$72.90	$72.90
Purchase #6	$187.49	5.224%	$197.2845	$197.28	$197.30	$197.30
Purchase #7	$247.86	7.666%	$266.8609	$266.86	$266.85	$266.90
7 purchase totals =	$871.32		$935.3050	$935.30	$935.30	$935.40