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	$109.64	10.283%	$120.9143	$120.91	$120.90	$120.90
Purchase #2	$82.41	4.244%	$85.9075	$85.91	$85.90	$85.90
Purchase #3	$115.76	3.469%	$119.7757	$119.78	$119.80	$119.80
Purchase #4	$218.86	11.152%	$243.2673	$243.27	$243.25	$243.30
Purchase #5	$173.60	10.564%	$191.9391	$191.94	$191.95	$191.90
Purchase #6	$249.65	5.205%	$262.6443	$262.64	$262.65	$262.60
Purchase #7	$153.70	8.816%	$167.2502	$167.25	$167.25	$167.30
7 purchase totals =	$1,103.62		$1,191.6984	$1,191.70	$1,191.70	$1,191.70