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	$58.88	6.790%	$62.878	$62.88	$62.90	$62.90
Purchase #2	$144.56	7.374%	$155.2199	$155.22	$155.20	$155.20
Purchase #3	$40.96	4.870%	$42.9548	$42.95	$42.95	$43.00
Purchase #4	$73.40	10.157%	$80.8552	$80.86	$80.85	$80.90
Purchase #5	$235.93	3.752%	$244.7821	$244.78	$244.80	$244.80
Purchase #6	$88.89	10.307%	$98.0519	$98.05	$98.05	$98.10
Purchase #7	$225.70	12.107%	$253.0255	$253.03	$253.05	$253.00
7 purchase totals =	$868.32		$937.7674	$937.77	$937.80	$937.90