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	$206.32	6.143%	$218.9942	$218.99	$219.00	$219.00
Purchase #2	$182.81	4.713%	$191.4258	$191.43	$191.45	$191.40
Purchase #3	$154.28	4.282%	$160.8863	$160.89	$160.90	$160.90
Purchase #4	$29.56	13.450%	$33.5358	$33.54	$33.55	$33.50
Purchase #5	$98.52	11.380%	$109.7316	$109.73	$109.75	$109.70
Purchase #6	$108.45	4.433%	$113.2576	$113.26	$113.25	$113.30
Purchase #7	$210.64	5.313%	$221.8313	$221.83	$221.85	$221.80
7 purchase totals =	$990.58		$1,049.6626	$1,049.67	$1,049.75	$1,049.60