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	$160.49	11.817%	$179.4551	$179.46	$179.45	$179.50
Purchase #2	$39.59	11.168%	$44.0114	$44.01	$44.00	$44.00
Purchase #3	$146.68	3.523%	$151.8475	$151.85	$151.85	$151.80
Purchase #4	$68.96	13.772%	$78.4572	$78.46	$78.45	$78.50
Purchase #5	$233.90	3.588%	$242.2923	$242.29	$242.30	$242.30
Purchase #6	$79.63	9.594%	$87.2697	$87.27	$87.25	$87.30
Purchase #7	$55.35	12.424%	$62.2267	$62.23	$62.25	$62.20
7 purchase totals =	$784.60		$845.5599	$845.57	$845.55	$845.60