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	$165.83	11.830%	$185.4477	$185.45	$185.45	$185.40
Purchase #2	$91.89	4.432%	$95.9626	$95.96	$95.95	$96.00
Purchase #3	$98.79	12.796%	$111.4312	$111.43	$111.45	$111.40
Purchase #4	$11.48	4.633%	$12.0119	$12.01	$12.00	$12.00
Purchase #5	$169.40	8.497%	$183.7939	$183.79	$183.80	$183.80
Purchase #6	$175.73	5.508%	$185.4092	$185.41	$185.40	$185.40
Purchase #7	$158.97	10.397%	$175.4981	$175.50	$175.50	$175.50
7 purchase totals =	$872.09		$949.5546	$949.55	$949.55	$949.50