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	$102.77	6.523%	$109.4737	$109.47	$109.45	$109.50
Purchase #2	$174.49	9.344%	$190.7943	$190.79	$190.80	$190.80
Purchase #3	$64.89	12.267%	$72.8501	$72.85	$72.85	$72.90
Purchase #4	$168.54	12.511%	$189.626	$189.63	$189.65	$189.60
Purchase #5	$182.43	3.683%	$189.1489	$189.15	$189.15	$189.10
Purchase #6	$218.76	9.286%	$239.0741	$239.07	$239.05	$239.10
Purchase #7	$44.85	5.203%	$47.1835	$47.18	$47.20	$47.20
7 purchase totals =	$956.73		$1,038.1506	$1,038.14	$1,038.15	$1,038.20