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	$225.40	11.139%	$250.5073	$250.51	$250.50	$250.50
Purchase #2	$139.99	5.462%	$147.6363	$147.64	$147.65	$147.60
Purchase #3	$55.76	6.835%	$59.5712	$59.57	$59.55	$59.60
Purchase #4	$136.50	6.463%	$145.322	$145.32	$145.30	$145.30
Purchase #5	$194.83	8.178%	$210.7632	$210.76	$210.75	$210.80
Purchase #6	$100.36	3.150%	$103.5213	$103.52	$103.50	$103.50
Purchase #7	$202.78	13.239%	$229.626	$229.63	$229.65	$229.60
7 purchase totals =	$1,055.62		$1,146.9473	$1,146.95	$1,146.90	$1,146.90