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	$134.90	11.295%	$150.137	$150.14	$150.15	$150.10
Purchase #2	$211.91	11.430%	$236.1313	$236.13	$236.15	$236.10
Purchase #3	$149.27	8.730%	$162.3013	$162.30	$162.30	$162.30
Purchase #4	$211.39	10.841%	$234.3068	$234.31	$234.30	$234.30
Purchase #5	$80.34	12.623%	$90.4813	$90.48	$90.50	$90.50
Purchase #6	$144.34	3.190%	$148.9444	$148.94	$148.95	$148.90
Purchase #7	$30.60	4.342%	$31.9287	$31.93	$31.95	$31.90
7 purchase totals =	$962.75		$1,054.2308	$1,054.23	$1,054.30	$1,054.10