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	$59.38	13.675%	$67.5002	$67.50	$67.50	$67.50
Purchase #2	$78.66	3.188%	$81.1677	$81.17	$81.15	$81.20
Purchase #3	$59.92	3.337%	$61.9195	$61.92	$61.90	$61.90
Purchase #4	$53.36	4.143%	$55.5707	$55.57	$55.55	$55.60
Purchase #5	$143.34	7.507%	$154.1005	$154.10	$154.10	$154.10
Purchase #6	$127.28	5.199%	$133.8973	$133.90	$133.90	$133.90
Purchase #7	$189.67	11.611%	$211.6926	$211.69	$211.70	$211.70
7 purchase totals =	$711.61		$765.8485	$765.85	$765.80	$765.90