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	$118.35	5.421%	$124.7658	$124.77	$124.75	$124.80
Purchase #2	$189.86	3.698%	$196.881	$196.88	$196.90	$196.90
Purchase #3	$65.54	11.826%	$73.2908	$73.29	$73.30	$73.30
Purchase #4	$240.91	9.538%	$263.888	$263.89	$263.90	$263.90
Purchase #5	$42.72	11.315%	$47.5538	$47.55	$47.55	$47.60
Purchase #6	$143.90	6.680%	$153.5125	$153.51	$153.50	$153.50
Purchase #7	$136.71	5.492%	$144.2181	$144.22	$144.20	$144.20
7 purchase totals =	$937.99		$1,004.1100	$1,004.11	$1,004.10	$1,004.20