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	$242.91	10.167%	$267.6067	$267.61	$267.60	$267.60
Purchase #2	$90.33	11.661%	$100.8634	$100.86	$100.85	$100.90
Purchase #3	$243.71	4.205%	$253.958	$253.96	$253.95	$254.00
Purchase #4	$192.82	10.455%	$212.9793	$212.98	$213.00	$213.00
Purchase #5	$185.31	9.180%	$202.3215	$202.32	$202.30	$202.30
Purchase #6	$238.75	7.612%	$256.9237	$256.92	$256.90	$256.90
Purchase #7	$50.37	7.851%	$54.3245	$54.32	$54.30	$54.30
7 purchase totals =	$1,244.20		$1,348.9771	$1,348.97	$1,348.90	$1,349.00