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	$89.77	4.728%	$94.0143	$94.01	$94.00	$94.00
Purchase #2	$41.41	7.448%	$44.4942	$44.49	$44.50	$44.50
Purchase #3	$56.62	9.291%	$61.8806	$61.88	$61.90	$61.90
Purchase #4	$146.62	6.501%	$156.1518	$156.15	$156.15	$156.20
Purchase #5	$72.81	13.641%	$82.742	$82.74	$82.75	$82.70
Purchase #6	$92.89	4.575%	$97.1397	$97.14	$97.15	$97.10
Purchase #7	$6.46	9.672%	$7.0848	$7.08	$7.10	$7.10
7 purchase totals =	$506.58		$543.5074	$543.49	$543.55	$543.50