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	$47.25	9.731%	$51.8479	$51.85	$51.85	$51.80
Purchase #2	$28.72	8.666%	$31.2089	$31.21	$31.20	$31.20
Purchase #3	$89.48	5.522%	$94.4211	$94.42	$94.40	$94.40
Purchase #4	$151.41	5.830%	$160.2372	$160.24	$160.25	$160.20
Purchase #5	$137.49	3.824%	$142.7476	$142.75	$142.75	$142.70
Purchase #6	$65.49	9.677%	$71.8275	$71.83	$71.85	$71.80
Purchase #7	$153.73	13.334%	$174.2284	$174.23	$174.25	$174.20
7 purchase totals =	$673.57		$726.5186	$726.53	$726.55	$726.30