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	$188.48	11.169%	$209.5313	$209.53	$209.55	$209.50
Purchase #2	$243.90	9.506%	$267.0851	$267.09	$267.10	$267.10
Purchase #3	$19.79	12.551%	$22.2738	$22.27	$22.25	$22.30
Purchase #4	$129.36	10.639%	$143.1226	$143.12	$143.10	$143.10
Purchase #5	$69.50	12.722%	$78.3418	$78.34	$78.35	$78.30
Purchase #6	$155.55	4.649%	$162.7815	$162.78	$162.80	$162.80
Purchase #7	$241.92	8.451%	$262.3647	$262.36	$262.35	$262.40
7 purchase totals =	$1,048.50		$1,145.5008	$1,145.49	$1,145.50	$1,145.50