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	$218.46	9.206%	$238.5714	$238.57	$238.55	$238.60
Purchase #2	$205.47	4.191%	$214.0812	$214.08	$214.10	$214.10
Purchase #3	$71.56	13.374%	$81.1304	$81.13	$81.15	$81.10
Purchase #4	$49.41	8.793%	$53.7546	$53.75	$53.75	$53.80
Purchase #5	$248.75	4.182%	$259.1527	$259.15	$259.15	$259.20
Purchase #6	$196.81	13.234%	$222.8558	$222.86	$222.85	$222.90
Purchase #7	$210.87	7.785%	$227.2862	$227.29	$227.30	$227.30
7 purchase totals =	$1,201.33		$1,296.8323	$1,296.83	$1,296.85	$1,297.00