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	$222.70	8.434%	$241.4825	$241.48	$241.50	$241.50
Purchase #2	$91.59	5.840%	$96.9389	$96.94	$96.95	$96.90
Purchase #3	$196.96	7.413%	$211.5606	$211.56	$211.55	$211.60
Purchase #4	$21.34	5.354%	$22.4825	$22.48	$22.50	$22.50
Purchase #5	$174.87	3.183%	$180.4361	$180.44	$180.45	$180.40
Purchase #6	$178.64	7.619%	$192.2506	$192.25	$192.25	$192.30
Purchase #7	$92.96	8.342%	$100.7147	$100.71	$100.70	$100.70
7 purchase totals =	$979.06		$1,045.8659	$1,045.86	$1,045.90	$1,045.90