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	$156.56	12.570%	$176.2396	$176.24	$176.25	$176.20
Purchase #2	$155.70	7.493%	$167.3666	$167.37	$167.35	$167.40
Purchase #3	$32.86	7.799%	$35.4228	$35.42	$35.40	$35.40
Purchase #4	$226.98	5.443%	$239.3345	$239.33	$239.35	$239.30
Purchase #5	$87.93	9.117%	$95.9466	$95.95	$95.95	$95.90
Purchase #6	$230.56	5.209%	$242.5699	$242.57	$242.55	$242.60
Purchase #7	$98.37	13.126%	$111.282	$111.28	$111.30	$111.30
7 purchase totals =	$988.96		$1,068.1620	$1,068.16	$1,068.15	$1,068.10