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	$76.98	4.560%	$80.4903	$80.49	$80.50	$80.50
Purchase #2	$85.34	12.116%	$95.6798	$95.68	$95.70	$95.70
Purchase #3	$127.67	12.194%	$143.2381	$143.24	$143.25	$143.20
Purchase #4	$187.37	12.517%	$210.8231	$210.82	$210.80	$210.80
Purchase #5	$42.78	4.620%	$44.7564	$44.76	$44.75	$44.80
Purchase #6	$85.83	6.340%	$91.2716	$91.27	$91.25	$91.30
Purchase #7	$56.45	9.674%	$61.911	$61.91	$61.90	$61.90
7 purchase totals =	$662.42		$728.1703	$728.17	$728.15	$728.20