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	$183.54	10.211%	$202.2813	$202.28	$202.30	$202.30
Purchase #2	$47.83	9.865%	$52.5484	$52.55	$52.55	$52.50
Purchase #3	$76.86	6.834%	$82.1126	$82.11	$82.10	$82.10
Purchase #4	$215.30	10.776%	$238.5007	$238.50	$238.50	$238.50
Purchase #5	$107.96	7.230%	$115.7655	$115.77	$115.75	$115.80
Purchase #6	$213.59	6.404%	$227.2683	$227.27	$227.25	$227.30
Purchase #7	$80.54	6.336%	$85.643	$85.64	$85.65	$85.60
7 purchase totals =	$925.62		$1,004.1198	$1,004.12	$1,004.10	$1,004.10