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	$40.67	5.162%	$42.7694	$42.77	$42.75	$42.80
Purchase #2	$73.85	9.787%	$81.0777	$81.08	$81.10	$81.10
Purchase #3	$103.90	6.223%	$110.3657	$110.37	$110.35	$110.40
Purchase #4	$191.63	4.548%	$200.3453	$200.35	$200.35	$200.30
Purchase #5	$123.72	7.762%	$133.3231	$133.32	$133.30	$133.30
Purchase #6	$147.74	3.751%	$153.2817	$153.28	$153.30	$153.30
Purchase #7	$246.47	13.710%	$280.261	$280.26	$280.25	$280.30
7 purchase totals =	$927.98		$1,001.4239	$1,001.43	$1,001.40	$1,001.50