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	$186.43	5.195%	$196.115	$196.12	$196.10	$196.10
Purchase #2	$192.66	8.796%	$209.6064	$209.61	$209.60	$209.60
Purchase #3	$99.67	8.654%	$108.2954	$108.30	$108.30	$108.30
Purchase #4	$42.90	5.828%	$45.4002	$45.40	$45.40	$45.40
Purchase #5	$171.28	8.585%	$185.9844	$185.98	$186.00	$186.00
Purchase #6	$198.93	4.584%	$208.049	$208.05	$208.05	$208.00
Purchase #7	$88.85	7.265%	$95.305	$95.31	$95.30	$95.30
7 purchase totals =	$980.72		$1,048.7554	$1,048.77	$1,048.75	$1,048.70