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	$187.86	12.693%	$211.7051	$211.71	$211.70	$211.70
Purchase #2	$176.52	11.208%	$196.3044	$196.30	$196.30	$196.30
Purchase #3	$74.71	4.643%	$78.1788	$78.18	$78.20	$78.20
Purchase #4	$213.34	3.857%	$221.5685	$221.57	$221.55	$221.60
Purchase #5	$224.41	12.802%	$253.139	$253.14	$253.15	$253.10
Purchase #6	$57.90	6.440%	$61.6288	$61.63	$61.65	$61.60
Purchase #7	$194.30	12.401%	$218.3951	$218.40	$218.40	$218.40
7 purchase totals =	$1,129.04		$1,240.9197	$1,240.93	$1,240.95	$1,240.90