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	$199.83	4.700%	$209.222	$209.22	$209.20	$209.20
Purchase #2	$36.88	5.307%	$38.8372	$38.84	$38.85	$38.80
Purchase #3	$184.52	3.358%	$190.7162	$190.72	$190.70	$190.70
Purchase #4	$91.83	9.199%	$100.2774	$100.28	$100.30	$100.30
Purchase #5	$194.71	13.575%	$221.1419	$221.14	$221.15	$221.10
Purchase #6	$172.87	6.780%	$184.5906	$184.59	$184.60	$184.60
Purchase #7	$194.51	8.705%	$211.4421	$211.44	$211.45	$211.40
7 purchase totals =	$1,075.15		$1,156.2274	$1,156.23	$1,156.25	$1,156.10