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	$119.39	4.609%	$124.8927	$124.89	$124.90	$124.90
Purchase #2	$79.72	8.444%	$86.4516	$86.45	$86.45	$86.50
Purchase #3	$88.54	12.295%	$99.426	$99.43	$99.45	$99.40
Purchase #4	$43.25	7.515%	$46.5002	$46.50	$46.50	$46.50
Purchase #5	$121.36	8.582%	$131.7751	$131.78	$131.80	$131.80
Purchase #6	$128.45	12.740%	$144.8145	$144.81	$144.80	$144.80
Purchase #7	$184.31	3.685%	$191.1018	$191.10	$191.10	$191.10
7 purchase totals =	$765.02		$824.9619	$824.96	$825.00	$825.00