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	$115.79	6.344%	$123.1357	$123.14	$123.15	$123.10
Purchase #2	$141.45	10.671%	$156.5441	$156.54	$156.55	$156.50
Purchase #3	$208.69	4.296%	$217.6553	$217.66	$217.65	$217.70
Purchase #4	$122.41	6.462%	$130.3201	$130.32	$130.30	$130.30
Purchase #5	$220.32	10.388%	$243.2068	$243.21	$243.20	$243.20
Purchase #6	$182.82	8.280%	$197.9575	$197.96	$197.95	$198.00
Purchase #7	$90.38	9.650%	$99.1017	$99.10	$99.10	$99.10
7 purchase totals =	$1,081.86		$1,167.9212	$1,167.93	$1,167.90	$1,167.90