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	$186.46	6.691%	$198.936	$198.94	$198.95	$198.90
Purchase #2	$132.64	13.514%	$150.565	$150.57	$150.55	$150.60
Purchase #3	$57.28	3.774%	$59.4417	$59.44	$59.45	$59.40
Purchase #4	$130.38	9.290%	$142.4923	$142.49	$142.50	$142.50
Purchase #5	$64.84	3.657%	$67.2112	$67.21	$67.20	$67.20
Purchase #6	$96.27	13.662%	$109.4224	$109.42	$109.40	$109.40
Purchase #7	$244.43	6.591%	$260.5404	$260.54	$260.55	$260.50
7 purchase totals =	$912.30		$988.6090	$988.61	$988.60	$988.50