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	$122.50	11.690%	$136.8203	$136.82	$136.80	$136.80
Purchase #2	$57.67	11.466%	$64.2824	$64.28	$64.30	$64.30
Purchase #3	$215.49	3.857%	$223.8014	$223.80	$223.80	$223.80
Purchase #4	$123.98	8.507%	$134.527	$134.53	$134.55	$134.50
Purchase #5	$83.27	4.265%	$86.8215	$86.82	$86.80	$86.80
Purchase #6	$140.89	8.539%	$152.9206	$152.92	$152.90	$152.90
Purchase #7	$231.55	7.188%	$248.1938	$248.19	$248.20	$248.20
7 purchase totals =	$975.35		$1,047.3670	$1,047.36	$1,047.35	$1,047.30