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	$232.97	9.829%	$255.8686	$255.87	$255.85	$255.90
Purchase #2	$78.29	5.186%	$82.3501	$82.35	$82.35	$82.40
Purchase #3	$189.50	5.108%	$199.1797	$199.18	$199.20	$199.20
Purchase #4	$118.73	4.334%	$123.8758	$123.88	$123.90	$123.90
Purchase #5	$188.57	12.699%	$212.5165	$212.52	$212.50	$212.50
Purchase #6	$196.27	6.596%	$209.216	$209.22	$209.20	$209.20
Purchase #7	$146.46	5.489%	$154.4992	$154.50	$154.50	$154.50
7 purchase totals =	$1,150.79		$1,237.5059	$1,237.52	$1,237.50	$1,237.60