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	$175.93	5.688%	$185.9369	$185.94	$185.95	$185.90
Purchase #2	$175.70	13.382%	$199.2122	$199.21	$199.20	$199.20
Purchase #3	$233.47	13.729%	$265.5231	$265.52	$265.50	$265.50
Purchase #4	$75.94	4.657%	$79.4765	$79.48	$79.50	$79.50
Purchase #5	$174.40	12.555%	$196.2959	$196.30	$196.30	$196.30
Purchase #6	$215.73	3.641%	$223.5847	$223.58	$223.60	$223.60
Purchase #7	$53.63	3.167%	$55.3285	$55.33	$55.35	$55.30
7 purchase totals =	$1,104.80		$1,205.3578	$1,205.36	$1,205.40	$1,205.30