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	$162.81	11.687%	$181.8376	$181.84	$181.85	$181.80
Purchase #2	$174.32	11.230%	$193.8961	$193.90	$193.90	$193.90
Purchase #3	$175.81	5.342%	$185.2018	$185.20	$185.20	$185.20
Purchase #4	$54.32	6.521%	$57.8622	$57.86	$57.85	$57.90
Purchase #5	$194.71	6.267%	$206.9125	$206.91	$206.90	$206.90
Purchase #6	$31.31	8.263%	$33.8971	$33.90	$33.90	$33.90
Purchase #7	$16.49	9.179%	$18.0036	$18.00	$18.00	$18.00
7 purchase totals =	$809.77		$877.6109	$877.61	$877.60	$877.60