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	$65.66	7.476%	$70.5687	$70.57	$70.55	$70.60
Purchase #2	$204.75	11.260%	$227.8049	$227.80	$227.80	$227.80
Purchase #3	$29.89	5.863%	$31.6425	$31.64	$31.65	$31.60
Purchase #4	$199.41	11.283%	$221.9094	$221.91	$221.90	$221.90
Purchase #5	$190.26	13.670%	$216.2685	$216.27	$216.25	$216.30
Purchase #6	$164.29	10.383%	$181.3482	$181.35	$181.35	$181.30
Purchase #7	$203.97	9.403%	$223.1493	$223.15	$223.15	$223.10
7 purchase totals =	$1,058.23		$1,172.6915	$1,172.69	$1,172.65	$1,172.60