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	$156.45	3.668%	$162.1886	$162.19	$162.20	$162.20
Purchase #2	$219.59	12.463%	$246.9575	$246.96	$246.95	$247.00
Purchase #3	$144.30	3.526%	$149.388	$149.39	$149.40	$149.40
Purchase #4	$72.75	13.340%	$82.4549	$82.45	$82.45	$82.50
Purchase #5	$59.36	5.430%	$62.5832	$62.58	$62.60	$62.60
Purchase #6	$90.85	5.682%	$96.0121	$96.01	$96.00	$96.00
Purchase #7	$189.29	3.866%	$196.608	$196.61	$196.60	$196.60
7 purchase totals =	$932.59		$996.1923	$996.19	$996.20	$996.30