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	$123.81	3.332%	$127.9353	$127.94	$127.95	$127.90
Purchase #2	$52.73	10.732%	$58.389	$58.39	$58.40	$58.40
Purchase #3	$101.31	8.691%	$110.1149	$110.11	$110.10	$110.10
Purchase #4	$54.30	9.732%	$59.5845	$59.58	$59.60	$59.60
Purchase #5	$166.65	8.796%	$181.3085	$181.31	$181.30	$181.30
Purchase #6	$129.88	13.640%	$147.5956	$147.60	$147.60	$147.60
Purchase #7	$143.82	12.763%	$162.1757	$162.18	$162.20	$162.20
7 purchase totals =	$772.50		$847.1035	$847.11	$847.15	$847.10