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	$56.44	4.533%	$58.9984	$59.00	$59.00	$59.00
Purchase #2	$189.33	5.481%	$199.7072	$199.71	$199.70	$199.70
Purchase #3	$73.43	6.331%	$78.0789	$78.08	$78.10	$78.10
Purchase #4	$85.63	4.405%	$89.402	$89.40	$89.40	$89.40
Purchase #5	$58.60	11.647%	$65.4251	$65.43	$65.45	$65.40
Purchase #6	$190.87	10.409%	$210.7377	$210.74	$210.75	$210.70
Purchase #7	$92.92	3.382%	$96.0626	$96.06	$96.05	$96.10
7 purchase totals =	$747.22		$798.4119	$798.42	$798.45	$798.40