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	$30.59	6.590%	$32.6059	$32.61	$32.60	$32.60
Purchase #2	$234.79	5.199%	$246.9967	$247.00	$247.00	$247.00
Purchase #3	$90.33	10.629%	$99.9312	$99.93	$99.95	$99.90
Purchase #4	$157.92	10.775%	$174.9359	$174.94	$174.95	$174.90
Purchase #5	$134.87	7.822%	$145.4195	$145.42	$145.40	$145.40
Purchase #6	$160.34	4.108%	$166.9268	$166.93	$166.95	$166.90
Purchase #7	$139.55	11.293%	$155.3094	$155.31	$155.30	$155.30
7 purchase totals =	$948.39		$1,022.1254	$1,022.14	$1,022.15	$1,022.00