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	$204.59	3.423%	$211.5931	$211.59	$211.60	$211.60
Purchase #2	$194.40	4.612%	$203.3657	$203.37	$203.35	$203.40
Purchase #3	$53.72	5.689%	$56.7761	$56.78	$56.80	$56.80
Purchase #4	$57.51	7.520%	$61.8348	$61.83	$61.85	$61.80
Purchase #5	$53.59	12.657%	$60.3729	$60.37	$60.35	$60.40
Purchase #6	$99.36	10.162%	$109.457	$109.46	$109.45	$109.50
Purchase #7	$69.79	12.132%	$78.2569	$78.26	$78.25	$78.30
7 purchase totals =	$732.96		$781.6565	$781.66	$781.65	$781.80