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	$55.54	10.131%	$61.1668	$61.17	$61.15	$61.20
Purchase #2	$204.47	5.776%	$216.2802	$216.28	$216.30	$216.30
Purchase #3	$205.29	12.812%	$231.5918	$231.59	$231.60	$231.60
Purchase #4	$58.41	11.769%	$65.2843	$65.28	$65.30	$65.30
Purchase #5	$87.85	3.720%	$91.118	$91.12	$91.10	$91.10
Purchase #6	$183.70	6.630%	$195.8793	$195.88	$195.90	$195.90
Purchase #7	$220.76	6.376%	$234.8357	$234.84	$234.85	$234.80
7 purchase totals =	$1,016.02		$1,096.1561	$1,096.16	$1,096.20	$1,096.20