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	$48.92	10.181%	$53.9005	$53.90	$53.90	$53.90
Purchase #2	$197.81	12.436%	$222.4097	$222.41	$222.40	$222.40
Purchase #3	$156.51	5.399%	$164.96	$164.96	$164.95	$165.00
Purchase #4	$181.61	12.483%	$204.2804	$204.28	$204.30	$204.30
Purchase #5	$108.86	11.175%	$121.0251	$121.03	$121.05	$121.00
Purchase #6	$136.97	10.642%	$151.5463	$151.55	$151.55	$151.50
Purchase #7	$245.25	4.210%	$255.575	$255.58	$255.60	$255.60
7 purchase totals =	$1,075.93		$1,173.6970	$1,173.71	$1,173.75	$1,173.70