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	$120.98	9.401%	$132.3533	$132.35	$132.35	$132.40
Purchase #2	$78.55	7.559%	$84.4876	$84.49	$84.50	$84.50
Purchase #3	$89.45	10.673%	$98.997	$99.00	$99.00	$99.00
Purchase #4	$58.88	6.808%	$62.8886	$62.89	$62.90	$62.90
Purchase #5	$105.99	6.454%	$112.8306	$112.83	$112.85	$112.80
Purchase #6	$218.46	12.341%	$245.4201	$245.42	$245.40	$245.40
Purchase #7	$136.38	7.358%	$146.4148	$146.41	$146.40	$146.40
7 purchase totals =	$808.69		$883.3920	$883.39	$883.40	$883.40