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	$51.56	3.709%	$53.4724	$53.47	$53.45	$53.50
Purchase #2	$196.81	12.391%	$221.1967	$221.20	$221.20	$221.20
Purchase #3	$178.38	5.698%	$188.5441	$188.54	$188.55	$188.50
Purchase #4	$130.88	5.333%	$137.8598	$137.86	$137.85	$137.90
Purchase #5	$109.62	6.111%	$116.3189	$116.32	$116.30	$116.30
Purchase #6	$141.68	3.779%	$147.0341	$147.03	$147.05	$147.00
Purchase #7	$166.71	10.561%	$184.3162	$184.32	$184.30	$184.30
7 purchase totals =	$975.64		$1,048.7422	$1,048.74	$1,048.70	$1,048.70