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	$233.85	5.492%	$246.693	$246.69	$246.70	$246.70
Purchase #2	$143.89	11.282%	$160.1237	$160.12	$160.10	$160.10
Purchase #3	$92.46	7.665%	$99.5471	$99.55	$99.55	$99.50
Purchase #4	$203.93	12.683%	$229.7944	$229.79	$229.80	$229.80
Purchase #5	$151.47	10.561%	$167.4667	$167.47	$167.45	$167.50
Purchase #6	$43.64	10.305%	$48.1371	$48.14	$48.15	$48.10
Purchase #7	$209.57	4.242%	$218.46	$218.46	$218.45	$218.50
7 purchase totals =	$1,078.81		$1,170.2220	$1,170.22	$1,170.20	$1,170.20