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	$181.60	6.103%	$192.683	$192.68	$192.70	$192.70
Purchase #2	$213.72	12.544%	$240.529	$240.53	$240.55	$240.50
Purchase #3	$120.80	8.306%	$130.8336	$130.83	$130.85	$130.80
Purchase #4	$90.93	10.753%	$100.7077	$100.71	$100.70	$100.70
Purchase #5	$249.78	5.830%	$264.3422	$264.34	$264.35	$264.30
Purchase #6	$140.63	9.313%	$153.7269	$153.73	$153.75	$153.70
Purchase #7	$62.94	7.445%	$67.6259	$67.63	$67.65	$67.60
7 purchase totals =	$1,060.40		$1,150.4483	$1,150.45	$1,150.55	$1,150.30