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	$230.35	9.329%	$251.8394	$251.84	$251.85	$251.80
Purchase #2	$119.90	6.169%	$127.2966	$127.30	$127.30	$127.30
Purchase #3	$75.44	4.532%	$78.8589	$78.86	$78.85	$78.90
Purchase #4	$155.28	4.636%	$162.4788	$162.48	$162.50	$162.50
Purchase #5	$91.87	7.586%	$98.8393	$98.84	$98.85	$98.80
Purchase #6	$111.76	4.396%	$116.673	$116.67	$116.65	$116.70
Purchase #7	$247.39	13.234%	$280.1296	$280.13	$280.15	$280.10
7 purchase totals =	$1,031.99		$1,116.1156	$1,116.12	$1,116.15	$1,116.10