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	$143.34	9.364%	$156.7624	$156.76	$156.75	$156.80
Purchase #2	$79.93	4.455%	$83.4909	$83.49	$83.50	$83.50
Purchase #3	$55.36	7.336%	$59.4212	$59.42	$59.40	$59.40
Purchase #4	$162.25	9.346%	$177.4139	$177.41	$177.40	$177.40
Purchase #5	$74.90	4.309%	$78.1274	$78.13	$78.15	$78.10
Purchase #6	$147.57	3.454%	$152.6671	$152.67	$152.65	$152.70
Purchase #7	$88.59	9.546%	$97.0468	$97.05	$97.05	$97.00
7 purchase totals =	$751.94		$804.9297	$804.93	$804.90	$804.90