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	$77.78	9.371%	$85.0688	$85.07	$85.05	$85.10
Purchase #2	$55.75	3.384%	$57.6366	$57.64	$57.65	$57.60
Purchase #3	$127.60	12.793%	$143.9239	$143.92	$143.90	$143.90
Purchase #4	$186.56	11.831%	$208.6319	$208.63	$208.65	$208.60
Purchase #5	$34.87	11.581%	$38.9083	$38.91	$38.90	$38.90
Purchase #6	$131.63	7.104%	$140.981	$140.98	$141.00	$141.00
Purchase #7	$209.72	4.385%	$218.9162	$218.92	$218.90	$218.90
7 purchase totals =	$823.91		$894.0667	$894.07	$894.05	$894.00