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	$120.63	5.340%	$127.0716	$127.07	$127.05	$127.10
Purchase #2	$122.45	4.463%	$127.9149	$127.91	$127.90	$127.90
Purchase #3	$6.82	11.415%	$7.5985	$7.60	$7.60	$7.60
Purchase #4	$134.88	9.310%	$147.4373	$147.44	$147.45	$147.40
Purchase #5	$215.76	3.295%	$222.8693	$222.87	$222.85	$222.90
Purchase #6	$139.76	10.749%	$154.7828	$154.78	$154.80	$154.80
Purchase #7	$200.84	7.438%	$215.7785	$215.78	$215.80	$215.80
7 purchase totals =	$941.14		$1,003.4529	$1,003.45	$1,003.45	$1,003.50