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	$96.88	13.627%	$110.0818	$110.08	$110.10	$110.10
Purchase #2	$222.42	8.543%	$241.4213	$241.42	$241.40	$241.40
Purchase #3	$11.48	3.320%	$11.8611	$11.86	$11.85	$11.90
Purchase #4	$46.83	4.266%	$48.8278	$48.83	$48.85	$48.80
Purchase #5	$96.41	4.226%	$100.4843	$100.48	$100.50	$100.50
Purchase #6	$61.46	10.361%	$67.8279	$67.83	$67.85	$67.80
Purchase #7	$148.69	9.524%	$162.8512	$162.85	$162.85	$162.90
7 purchase totals =	$684.17		$743.3554	$743.35	$743.40	$743.40