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	$48.88	6.466%	$52.0406	$52.04	$52.05	$52.00
Purchase #2	$195.37	13.497%	$221.7391	$221.74	$221.75	$221.70
Purchase #3	$231.38	5.158%	$243.3146	$243.31	$243.30	$243.30
Purchase #4	$212.35	4.333%	$221.5511	$221.55	$221.55	$221.60
Purchase #5	$30.26	4.573%	$31.6438	$31.64	$31.65	$31.60
Purchase #6	$118.50	4.223%	$123.5043	$123.50	$123.50	$123.50
Purchase #7	$153.58	4.513%	$160.5111	$160.51	$160.50	$160.50
7 purchase totals =	$990.32		$1,054.3046	$1,054.29	$1,054.30	$1,054.20