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	$63.91	5.572%	$67.4711	$67.47	$67.45	$67.50
Purchase #2	$31.36	6.219%	$33.3103	$33.31	$33.30	$33.30
Purchase #3	$40.94	11.488%	$45.6432	$45.64	$45.65	$45.60
Purchase #4	$182.84	8.446%	$198.2827	$198.28	$198.30	$198.30
Purchase #5	$96.73	5.121%	$101.6835	$101.68	$101.70	$101.70
Purchase #6	$233.54	13.735%	$265.6167	$265.62	$265.60	$265.60
Purchase #7	$172.58	10.596%	$190.8666	$190.87	$190.85	$190.90
7 purchase totals =	$821.90		$902.8741	$902.87	$902.85	$902.90