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	$86.71	3.330%	$89.5974	$89.60	$89.60	$89.60
Purchase #2	$166.31	5.597%	$175.6184	$175.62	$175.60	$175.60
Purchase #3	$96.88	11.261%	$107.7897	$107.79	$107.80	$107.80
Purchase #4	$59.63	8.796%	$64.8751	$64.88	$64.90	$64.90
Purchase #5	$38.36	13.435%	$43.5137	$43.51	$43.50	$43.50
Purchase #6	$162.93	5.278%	$171.5294	$171.53	$171.55	$171.50
Purchase #7	$124.87	6.346%	$132.7943	$132.79	$132.80	$132.80
7 purchase totals =	$735.69		$785.7180	$785.72	$785.75	$785.70