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	$25.94	3.415%	$26.8259	$26.83	$26.85	$26.80
Purchase #2	$93.73	12.355%	$105.3103	$105.31	$105.30	$105.30
Purchase #3	$62.81	13.176%	$71.0858	$71.09	$71.10	$71.10
Purchase #4	$80.75	11.609%	$90.1243	$90.12	$90.10	$90.10
Purchase #5	$154.30	9.396%	$168.798	$168.80	$168.80	$168.80
Purchase #6	$24.28	9.104%	$26.4905	$26.49	$26.50	$26.50
Purchase #7	$71.91	6.821%	$76.815	$76.82	$76.80	$76.80
7 purchase totals =	$513.72		$565.4498	$565.46	$565.45	$565.40