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	$93.32	3.473%	$96.561	$96.56	$96.55	$96.60
Purchase #2	$100.56	4.107%	$104.69	$104.69	$104.70	$104.70
Purchase #3	$78.73	4.696%	$82.4272	$82.43	$82.45	$82.40
Purchase #4	$87.54	12.679%	$98.6392	$98.64	$98.65	$98.60
Purchase #5	$99.93	4.619%	$104.5458	$104.55	$104.55	$104.50
Purchase #6	$210.99	13.772%	$240.0475	$240.05	$240.05	$240.00
Purchase #7	$243.65	10.317%	$268.7874	$268.79	$268.80	$268.80
7 purchase totals =	$914.72		$995.6981	$995.71	$995.75	$995.60