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	$222.58	4.483%	$232.5583	$232.56	$232.55	$232.60
Purchase #2	$205.38	11.238%	$228.4606	$228.46	$228.45	$228.50
Purchase #3	$124.31	5.813%	$131.5361	$131.54	$131.55	$131.50
Purchase #4	$114.82	3.649%	$119.0098	$119.01	$119.00	$119.00
Purchase #5	$51.65	3.670%	$53.5456	$53.55	$53.55	$53.50
Purchase #6	$244.69	5.395%	$257.891	$257.89	$257.90	$257.90
Purchase #7	$250.53	11.496%	$279.3309	$279.33	$279.35	$279.30
7 purchase totals =	$1,213.96		$1,302.3323	$1,302.34	$1,302.35	$1,302.30