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	$249.87	4.258%	$260.5095	$260.51	$260.50	$260.50
Purchase #2	$28.69	9.110%	$31.3037	$31.30	$31.30	$31.30
Purchase #3	$60.87	3.462%	$62.9773	$62.98	$63.00	$63.00
Purchase #4	$108.26	4.424%	$113.0494	$113.05	$113.05	$113.00
Purchase #5	$184.68	6.592%	$196.8541	$196.85	$196.85	$196.90
Purchase #6	$140.73	13.594%	$159.8608	$159.86	$159.85	$159.90
Purchase #7	$113.61	3.499%	$117.5852	$117.59	$117.60	$117.60
7 purchase totals =	$886.71		$942.1400	$942.14	$942.15	$942.20