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	$53.42	4.172%	$55.6487	$55.65	$55.65	$55.60
Purchase #2	$248.56	8.188%	$268.9121	$268.91	$268.90	$268.90
Purchase #3	$115.41	7.245%	$123.7715	$123.77	$123.75	$123.80
Purchase #4	$143.50	13.495%	$162.8653	$162.87	$162.85	$162.90
Purchase #5	$182.77	7.600%	$196.6605	$196.66	$196.65	$196.70
Purchase #6	$148.38	11.449%	$165.368	$165.37	$165.35	$165.40
Purchase #7	$113.60	8.295%	$123.0231	$123.02	$123.00	$123.00
7 purchase totals =	$1,005.64		$1,096.2492	$1,096.25	$1,096.15	$1,096.30