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	$197.29	9.159%	$215.3598	$215.36	$215.35	$215.40
Purchase #2	$120.32	12.240%	$135.0472	$135.05	$135.05	$135.00
Purchase #3	$152.94	13.851%	$174.1237	$174.12	$174.10	$174.10
Purchase #4	$160.25	4.552%	$167.5446	$167.54	$167.55	$167.50
Purchase #5	$178.37	3.708%	$184.984	$184.98	$185.00	$185.00
Purchase #6	$83.97	6.495%	$89.4239	$89.42	$89.40	$89.40
Purchase #7	$237.69	10.589%	$262.859	$262.86	$262.85	$262.90
7 purchase totals =	$1,130.83		$1,229.3422	$1,229.33	$1,229.30	$1,229.30