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	$208.36	6.705%	$222.3305	$222.33	$222.35	$222.30
Purchase #2	$60.41	6.706%	$64.4611	$64.46	$64.45	$64.50
Purchase #3	$56.31	5.554%	$59.4375	$59.44	$59.45	$59.40
Purchase #4	$159.57	10.221%	$175.8796	$175.88	$175.90	$175.90
Purchase #5	$121.60	4.553%	$127.1364	$127.14	$127.15	$127.10
Purchase #6	$142.25	12.760%	$160.4011	$160.40	$160.40	$160.40
Purchase #7	$201.95	13.184%	$228.5751	$228.58	$228.60	$228.60
7 purchase totals =	$950.45		$1,038.2213	$1,038.23	$1,038.30	$1,038.20