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	$219.93	3.150%	$226.8578	$226.86	$226.85	$226.90
Purchase #2	$240.57	3.353%	$248.6363	$248.64	$248.65	$248.60
Purchase #3	$188.63	7.874%	$203.4827	$203.48	$203.50	$203.50
Purchase #4	$95.96	8.318%	$103.942	$103.94	$103.95	$103.90
Purchase #5	$92.76	11.700%	$103.6129	$103.61	$103.60	$103.60
Purchase #6	$79.37	9.377%	$86.8125	$86.81	$86.80	$86.80
Purchase #7	$233.67	9.751%	$256.4552	$256.46	$256.45	$256.50
7 purchase totals =	$1,150.89		$1,229.7994	$1,229.80	$1,229.80	$1,229.80