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	$78.45	13.798%	$89.2745	$89.27	$89.25	$89.30
Purchase #2	$237.59	7.413%	$255.2025	$255.20	$255.20	$255.20
Purchase #3	$213.37	5.166%	$224.3927	$224.39	$224.40	$224.40
Purchase #4	$197.60	7.502%	$212.424	$212.42	$212.40	$212.40
Purchase #5	$119.26	6.535%	$127.0536	$127.05	$127.05	$127.10
Purchase #6	$196.36	4.835%	$205.854	$205.85	$205.85	$205.90
Purchase #7	$50.40	3.463%	$52.1454	$52.15	$52.15	$52.10
7 purchase totals =	$1,093.03		$1,166.3467	$1,166.33	$1,166.30	$1,166.40