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	$33.63	11.699%	$37.5644	$37.56	$37.55	$37.60
Purchase #2	$163.41	10.539%	$180.6318	$180.63	$180.65	$180.60
Purchase #3	$175.75	3.488%	$181.8802	$181.88	$181.90	$181.90
Purchase #4	$58.67	6.561%	$62.5193	$62.52	$62.50	$62.50
Purchase #5	$209.27	3.275%	$216.1236	$216.12	$216.10	$216.10
Purchase #6	$12.92	12.630%	$14.5518	$14.55	$14.55	$14.60
Purchase #7	$82.91	5.716%	$87.6491	$87.65	$87.65	$87.60
7 purchase totals =	$736.56		$780.9202	$780.91	$780.90	$780.90