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	$85.98	12.753%	$96.945	$96.95	$96.95	$96.90
Purchase #2	$155.90	6.751%	$166.4248	$166.42	$166.40	$166.40
Purchase #3	$207.47	8.435%	$224.9701	$224.97	$224.95	$225.00
Purchase #4	$201.29	9.510%	$220.4327	$220.43	$220.45	$220.40
Purchase #5	$55.57	7.225%	$59.5849	$59.58	$59.60	$59.60
Purchase #6	$200.31	12.678%	$225.7053	$225.71	$225.70	$225.70
Purchase #7	$149.55	4.642%	$156.4921	$156.49	$156.50	$156.50
7 purchase totals =	$1,056.07		$1,150.5549	$1,150.55	$1,150.55	$1,150.50