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	$31.36	12.432%	$35.2587	$35.26	$35.25	$35.30
Purchase #2	$64.55	13.429%	$73.2184	$73.22	$73.20	$73.20
Purchase #3	$227.46	4.557%	$237.8254	$237.83	$237.85	$237.80
Purchase #4	$226.80	12.390%	$254.9005	$254.90	$254.90	$254.90
Purchase #5	$222.51	9.590%	$243.8487	$243.85	$243.85	$243.80
Purchase #6	$105.39	13.481%	$119.5976	$119.60	$119.60	$119.60
Purchase #7	$46.39	9.156%	$50.6375	$50.64	$50.65	$50.60
7 purchase totals =	$924.46		$1,015.2868	$1,015.30	$1,015.30	$1,015.20