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	$90.73	4.650%	$94.9489	$94.95	$94.95	$94.90
Purchase #2	$127.85	9.724%	$140.2821	$140.28	$140.30	$140.30
Purchase #3	$75.75	3.705%	$78.5565	$78.56	$78.55	$78.60
Purchase #4	$159.63	6.415%	$169.8703	$169.87	$169.85	$169.90
Purchase #5	$136.76	3.794%	$141.9487	$141.95	$141.95	$141.90
Purchase #6	$222.49	7.321%	$238.7785	$238.78	$238.80	$238.80
Purchase #7	$13.43	3.540%	$13.9054	$13.91	$13.90	$13.90
7 purchase totals =	$826.64		$878.2904	$878.30	$878.30	$878.30