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	$91.67	7.822%	$98.8404	$98.84	$98.85	$98.80
Purchase #2	$193.66	8.701%	$210.5104	$210.51	$210.50	$210.50
Purchase #3	$199.25	11.630%	$222.4228	$222.42	$222.40	$222.40
Purchase #4	$83.83	11.794%	$93.7169	$93.72	$93.70	$93.70
Purchase #5	$55.74	6.334%	$59.2706	$59.27	$59.25	$59.30
Purchase #6	$220.32	11.241%	$245.0862	$245.09	$245.10	$245.10
Purchase #7	$187.40	5.866%	$198.3929	$198.39	$198.40	$198.40
7 purchase totals =	$1,031.87		$1,128.2402	$1,128.24	$1,128.20	$1,128.20