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	$143.33	7.452%	$154.011	$154.01	$154.00	$154.00
Purchase #2	$148.86	9.312%	$162.7218	$162.72	$162.70	$162.70
Purchase #3	$239.65	8.702%	$260.5043	$260.50	$260.50	$260.50
Purchase #4	$101.75	11.610%	$113.5632	$113.56	$113.55	$113.60
Purchase #5	$100.65	10.690%	$111.4095	$111.41	$111.40	$111.40
Purchase #6	$112.95	12.759%	$127.3613	$127.36	$127.35	$127.40
Purchase #7	$226.96	8.299%	$245.7954	$245.80	$245.80	$245.80
7 purchase totals =	$1,074.15		$1,175.3665	$1,175.36	$1,175.30	$1,175.40