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	$106.46	6.225%	$113.0871	$113.09	$113.10	$113.10
Purchase #2	$150.52	5.709%	$159.1132	$159.11	$159.10	$159.10
Purchase #3	$71.31	10.594%	$78.8646	$78.86	$78.85	$78.90
Purchase #4	$196.54	13.257%	$222.5953	$222.60	$222.60	$222.60
Purchase #5	$34.26	4.823%	$35.9124	$35.91	$35.90	$35.90
Purchase #6	$62.27	4.663%	$65.1737	$65.17	$65.15	$65.20
Purchase #7	$78.60	9.682%	$86.2101	$86.21	$86.20	$86.20
7 purchase totals =	$699.96		$760.9564	$760.95	$760.90	$761.00