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	$184.39	6.561%	$196.4878	$196.49	$196.50	$196.50
Purchase #2	$35.27	3.125%	$36.3722	$36.37	$36.35	$36.40
Purchase #3	$53.31	4.825%	$55.8822	$55.88	$55.90	$55.90
Purchase #4	$101.84	6.401%	$108.3588	$108.36	$108.35	$108.40
Purchase #5	$154.56	5.856%	$163.611	$163.61	$163.60	$163.60
Purchase #6	$86.51	11.289%	$96.2761	$96.28	$96.30	$96.30
Purchase #7	$100.63	10.420%	$111.1156	$111.12	$111.10	$111.10
7 purchase totals =	$716.51		$768.1037	$768.11	$768.10	$768.20