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	$96.62	4.503%	$100.9708	$100.97	$100.95	$101.00
Purchase #2	$242.78	6.729%	$259.1167	$259.12	$259.10	$259.10
Purchase #3	$198.87	4.872%	$208.5589	$208.56	$208.55	$208.60
Purchase #4	$100.38	3.453%	$103.8461	$103.85	$103.85	$103.80
Purchase #5	$10.79	5.235%	$11.3549	$11.35	$11.35	$11.40
Purchase #6	$71.51	13.623%	$81.2518	$81.25	$81.25	$81.30
Purchase #7	$243.87	12.298%	$273.8611	$273.86	$273.85	$273.90
7 purchase totals =	$964.82		$1,038.9603	$1,038.96	$1,038.90	$1,039.10