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	$177.61	4.339%	$185.3165	$185.32	$185.30	$185.30
Purchase #2	$197.57	10.224%	$217.7696	$217.77	$217.75	$217.80
Purchase #3	$150.30	11.841%	$168.097	$168.10	$168.10	$168.10
Purchase #4	$186.74	5.196%	$196.443	$196.44	$196.45	$196.40
Purchase #5	$75.86	9.139%	$82.7928	$82.79	$82.80	$82.80
Purchase #6	$209.43	11.343%	$233.1856	$233.19	$233.20	$233.20
Purchase #7	$38.25	12.689%	$43.1035	$43.10	$43.10	$43.10
7 purchase totals =	$1,035.76		$1,126.7080	$1,126.71	$1,126.70	$1,126.70