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	$39.82	10.650%	$44.0608	$44.06	$44.05	$44.10
Purchase #2	$169.29	3.555%	$175.3083	$175.31	$175.30	$175.30
Purchase #3	$185.32	13.534%	$210.4012	$210.40	$210.40	$210.40
Purchase #4	$248.27	5.477%	$261.8677	$261.87	$261.85	$261.90
Purchase #5	$42.65	3.833%	$44.2848	$44.28	$44.30	$44.30
Purchase #6	$82.53	3.490%	$85.4103	$85.41	$85.40	$85.40
Purchase #7	$157.88	9.232%	$172.4555	$172.46	$172.45	$172.50
7 purchase totals =	$925.76		$993.7886	$993.79	$993.75	$993.90