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	$176.82	6.528%	$188.3628	$188.36	$188.35	$188.40
Purchase #2	$174.71	4.529%	$182.6226	$182.62	$182.60	$182.60
Purchase #3	$201.34	3.322%	$208.0285	$208.03	$208.05	$208.00
Purchase #4	$147.36	7.822%	$158.8865	$158.89	$158.90	$158.90
Purchase #5	$48.46	7.148%	$51.9239	$51.92	$51.90	$51.90
Purchase #6	$130.64	3.272%	$134.9145	$134.91	$134.90	$134.90
Purchase #7	$212.83	4.541%	$222.4946	$222.49	$222.50	$222.50
7 purchase totals =	$1,092.16		$1,147.2334	$1,147.22	$1,147.20	$1,147.20