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	$225.25	8.761%	$244.9842	$244.98	$245.00	$245.00
Purchase #2	$142.38	7.601%	$153.2023	$153.20	$153.20	$153.20
Purchase #3	$70.77	8.663%	$76.9008	$76.90	$76.90	$76.90
Purchase #4	$190.86	12.292%	$214.3205	$214.32	$214.30	$214.30
Purchase #5	$241.81	4.178%	$251.9128	$251.91	$251.90	$251.90
Purchase #6	$88.88	11.131%	$98.7732	$98.77	$98.75	$98.80
Purchase #7	$52.59	13.474%	$59.676	$59.68	$59.70	$59.70
7 purchase totals =	$1,012.54		$1,099.7698	$1,099.76	$1,099.75	$1,099.80