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	$208.37	4.570%	$217.8925	$217.89	$217.90	$217.90
Purchase #2	$161.48	5.386%	$170.1773	$170.18	$170.20	$170.20
Purchase #3	$62.31	11.280%	$69.3386	$69.34	$69.35	$69.30
Purchase #4	$174.77	6.746%	$186.56	$186.56	$186.55	$186.60
Purchase #5	$128.28	13.620%	$145.7517	$145.75	$145.75	$145.80
Purchase #6	$114.39	8.148%	$123.7105	$123.71	$123.70	$123.70
Purchase #7	$185.97	6.662%	$198.3593	$198.36	$198.35	$198.40
7 purchase totals =	$1,035.57		$1,111.7899	$1,111.79	$1,111.80	$1,111.90