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	$162.96	13.533%	$185.0134	$185.01	$185.00	$185.00
Purchase #2	$37.44	13.683%	$42.5629	$42.56	$42.55	$42.60
Purchase #3	$149.82	10.752%	$165.9286	$165.93	$165.95	$165.90
Purchase #4	$186.66	6.371%	$198.5521	$198.55	$198.55	$198.60
Purchase #5	$49.77	3.623%	$51.5732	$51.57	$51.55	$51.60
Purchase #6	$169.31	12.372%	$190.257	$190.26	$190.25	$190.30
Purchase #7	$71.47	12.129%	$80.1386	$80.14	$80.15	$80.10
7 purchase totals =	$827.43		$914.0258	$914.02	$914.00	$914.10