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	$44.54	3.430%	$46.0677	$46.07	$46.05	$46.10
Purchase #2	$250.95	11.639%	$280.1581	$280.16	$280.15	$280.20
Purchase #3	$71.40	4.723%	$74.7722	$74.77	$74.75	$74.80
Purchase #4	$193.75	12.845%	$218.6372	$218.64	$218.65	$218.60
Purchase #5	$73.37	5.199%	$77.1845	$77.18	$77.20	$77.20
Purchase #6	$139.93	11.473%	$155.9842	$155.98	$156.00	$156.00
Purchase #7	$78.75	13.671%	$89.5159	$89.52	$89.50	$89.50
7 purchase totals =	$852.69		$942.3198	$942.32	$942.30	$942.40