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	$47.78	9.343%	$52.2441	$52.24	$52.25	$52.20
Purchase #2	$6.85	4.387%	$7.1505	$7.15	$7.15	$7.20
Purchase #3	$198.38	12.193%	$222.5685	$222.57	$222.55	$222.60
Purchase #4	$182.96	4.465%	$191.1292	$191.13	$191.15	$191.10
Purchase #5	$156.49	3.612%	$162.1424	$162.14	$162.15	$162.10
Purchase #6	$136.38	9.764%	$149.6961	$149.70	$149.70	$149.70
Purchase #7	$249.98	12.170%	$280.4026	$280.40	$280.40	$280.40
7 purchase totals =	$978.82		$1,065.3334	$1,065.33	$1,065.35	$1,065.30