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	$71.67	12.641%	$80.7298	$80.73	$80.75	$80.70
Purchase #2	$96.50	13.605%	$109.6288	$109.63	$109.65	$109.60
Purchase #3	$155.94	10.273%	$171.9597	$171.96	$171.95	$172.00
Purchase #4	$155.27	4.605%	$162.4202	$162.42	$162.40	$162.40
Purchase #5	$226.72	4.345%	$236.571	$236.57	$236.55	$236.60
Purchase #6	$43.52	3.507%	$45.0462	$45.05	$45.05	$45.00
Purchase #7	$184.87	7.472%	$198.6835	$198.68	$198.70	$198.70
7 purchase totals =	$934.49		$1,005.0392	$1,005.04	$1,005.05	$1,005.00