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	$200.40	4.223%	$208.8629	$208.86	$208.85	$208.90
Purchase #2	$237.61	5.481%	$250.6334	$250.63	$250.65	$250.60
Purchase #3	$62.41	8.413%	$67.6606	$67.66	$67.65	$67.70
Purchase #4	$124.57	13.443%	$141.3159	$141.32	$141.30	$141.30
Purchase #5	$174.39	11.579%	$194.5826	$194.58	$194.60	$194.60
Purchase #6	$63.28	12.755%	$71.3514	$71.35	$71.35	$71.40
Purchase #7	$207.62	4.729%	$217.4383	$217.44	$217.45	$217.40
7 purchase totals =	$1,070.28		$1,151.8451	$1,151.84	$1,151.85	$1,151.90