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	$62.83	9.549%	$68.8296	$68.83	$68.85	$68.80
Purchase #2	$47.60	5.793%	$50.3575	$50.36	$50.35	$50.40
Purchase #3	$189.77	3.446%	$196.3095	$196.31	$196.30	$196.30
Purchase #4	$6.25	4.347%	$6.5217	$6.52	$6.50	$6.50
Purchase #5	$47.42	12.240%	$53.2242	$53.22	$53.20	$53.20
Purchase #6	$202.30	4.513%	$211.4298	$211.43	$211.45	$211.40
Purchase #7	$137.89	3.313%	$142.4583	$142.46	$142.45	$142.50
7 purchase totals =	$694.06		$729.1306	$729.13	$729.10	$729.10