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	$241.59	9.131%	$263.6496	$263.65	$263.65	$263.60
Purchase #2	$187.37	13.337%	$212.3595	$212.36	$212.35	$212.40
Purchase #3	$72.41	4.255%	$75.491	$75.49	$75.50	$75.50
Purchase #4	$68.75	13.859%	$78.2781	$78.28	$78.30	$78.30
Purchase #5	$50.69	6.543%	$54.0066	$54.01	$54.00	$54.00
Purchase #6	$58.64	4.566%	$61.3175	$61.32	$61.30	$61.30
Purchase #7	$14.56	7.480%	$15.6491	$15.65	$15.65	$15.60
7 purchase totals =	$694.01		$760.7514	$760.76	$760.75	$760.70