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	$231.27	13.556%	$262.621	$262.62	$262.60	$262.60
Purchase #2	$77.29	7.180%	$82.8394	$82.84	$82.85	$82.80
Purchase #3	$158.59	4.136%	$165.1493	$165.15	$165.15	$165.10
Purchase #4	$31.35	9.527%	$34.3367	$34.34	$34.35	$34.30
Purchase #5	$250.80	6.822%	$267.9096	$267.91	$267.90	$267.90
Purchase #6	$125.75	4.354%	$131.2252	$131.23	$131.25	$131.20
Purchase #7	$127.48	6.203%	$135.3876	$135.39	$135.40	$135.40
7 purchase totals =	$1,002.53		$1,079.4688	$1,079.48	$1,079.50	$1,079.30