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	$167.86	9.781%	$184.2784	$184.28	$184.30	$184.30
Purchase #2	$35.87	7.147%	$38.4336	$38.43	$38.45	$38.40
Purchase #3	$89.93	6.407%	$95.6918	$95.69	$95.70	$95.70
Purchase #4	$137.75	3.546%	$142.6346	$142.63	$142.65	$142.60
Purchase #5	$29.66	12.383%	$33.3328	$33.33	$33.35	$33.30
Purchase #6	$154.74	8.784%	$168.3324	$168.33	$168.35	$168.30
Purchase #7	$127.70	4.452%	$133.3852	$133.39	$133.40	$133.40
7 purchase totals =	$743.51		$796.0888	$796.08	$796.20	$796.00