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	$184.44	9.420%	$201.8142	$201.81	$201.80	$201.80
Purchase #2	$57.57	3.317%	$59.4796	$59.48	$59.50	$59.50
Purchase #3	$97.56	12.462%	$109.7179	$109.72	$109.70	$109.70
Purchase #4	$209.30	12.202%	$234.8388	$234.84	$234.85	$234.80
Purchase #5	$27.63	3.466%	$28.5877	$28.59	$28.60	$28.60
Purchase #6	$195.33	7.472%	$209.9251	$209.93	$209.95	$209.90
Purchase #7	$141.27	7.766%	$152.241	$152.24	$152.25	$152.20
7 purchase totals =	$913.10		$996.6043	$996.61	$996.65	$996.50