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	$53.58	10.663%	$59.2932	$59.29	$59.30	$59.30
Purchase #2	$85.99	5.518%	$90.7349	$90.73	$90.75	$90.70
Purchase #3	$211.73	11.111%	$235.2553	$235.26	$235.25	$235.30
Purchase #4	$51.49	5.446%	$54.2941	$54.29	$54.30	$54.30
Purchase #5	$144.48	13.703%	$164.2781	$164.28	$164.30	$164.30
Purchase #6	$133.94	6.591%	$142.768	$142.77	$142.75	$142.80
Purchase #7	$192.35	10.858%	$213.2354	$213.24	$213.25	$213.20
7 purchase totals =	$873.56		$959.8590	$959.86	$959.90	$959.90