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	$224.85	5.202%	$236.5467	$236.55	$236.55	$236.50
Purchase #2	$85.90	4.308%	$89.6006	$89.60	$89.60	$89.60
Purchase #3	$95.89	4.187%	$99.9049	$99.90	$99.90	$99.90
Purchase #4	$96.48	4.541%	$100.8612	$100.86	$100.85	$100.90
Purchase #5	$214.78	7.263%	$230.3795	$230.38	$230.40	$230.40
Purchase #6	$72.41	4.223%	$75.4679	$75.47	$75.45	$75.50
Purchase #7	$107.74	7.534%	$115.8571	$115.86	$115.85	$115.90
7 purchase totals =	$898.05		$948.6179	$948.62	$948.60	$948.70