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	$243.69	12.217%	$273.4616	$273.46	$273.45	$273.50
Purchase #2	$186.78	12.701%	$210.5029	$210.50	$210.50	$210.50
Purchase #3	$71.33	9.601%	$78.1784	$78.18	$78.20	$78.20
Purchase #4	$87.30	7.588%	$93.9243	$93.92	$93.90	$93.90
Purchase #5	$147.42	12.511%	$165.8637	$165.86	$165.85	$165.90
Purchase #6	$130.88	10.435%	$144.5373	$144.54	$144.55	$144.50
Purchase #7	$191.53	5.268%	$201.6198	$201.62	$201.60	$201.60
7 purchase totals =	$1,058.93		$1,168.0880	$1,168.08	$1,168.05	$1,168.10