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	$41.70	4.503%	$43.5778	$43.58	$43.60	$43.60
Purchase #2	$22.59	4.139%	$23.525	$23.53	$23.55	$23.50
Purchase #3	$68.33	6.308%	$72.6403	$72.64	$72.65	$72.60
Purchase #4	$89.71	7.317%	$96.2741	$96.27	$96.25	$96.30
Purchase #5	$184.52	3.569%	$191.1055	$191.11	$191.10	$191.10
Purchase #6	$147.85	13.619%	$167.9857	$167.99	$168.00	$168.00
Purchase #7	$35.76	8.743%	$38.8865	$38.89	$38.90	$38.90
7 purchase totals =	$590.46		$633.9949	$634.01	$634.05	$634.00