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	$209.38	7.290%	$224.6438	$224.64	$224.65	$224.60
Purchase #2	$51.59	6.367%	$54.8747	$54.87	$54.85	$54.90
Purchase #3	$84.59	7.239%	$90.7135	$90.71	$90.70	$90.70
Purchase #4	$176.32	7.481%	$189.5105	$189.51	$189.50	$189.50
Purchase #5	$186.31	6.445%	$198.3177	$198.32	$198.30	$198.30
Purchase #6	$61.92	9.687%	$67.9182	$67.92	$67.90	$67.90
Purchase #7	$209.52	6.608%	$223.3651	$223.37	$223.35	$223.40
7 purchase totals =	$979.63		$1,049.3435	$1,049.34	$1,049.25	$1,049.30