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	$99.31	3.505%	$102.7908	$102.79	$102.80	$102.80
Purchase #2	$6.58	4.872%	$6.9006	$6.90	$6.90	$6.90
Purchase #3	$67.25	11.352%	$74.8842	$74.88	$74.90	$74.90
Purchase #4	$72.56	8.292%	$78.5767	$78.58	$78.60	$78.60
Purchase #5	$140.63	12.211%	$157.8023	$157.80	$157.80	$157.80
Purchase #6	$150.97	13.650%	$171.5774	$171.58	$171.60	$171.60
Purchase #7	$127.39	4.634%	$133.2933	$133.29	$133.30	$133.30
7 purchase totals =	$664.69		$725.8253	$725.82	$725.90	$725.90